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digitalmars.D - Calling method by name.

reply %u <fghf jhgjhb.com> writes:
I know is possible to create an object from its name. It's possible to
call a method from that object if the name is only known at runtime?

Would something like the following be possible?

string classname, methodname;
// Ask the user for class and method.
auto obj = Object.factory(classname);
invoke(methodname, obj, param1, param2);

Thanks
Feb 02 2011
next sibling parent reply Robert Clipsham <robert octarineparrot.com> writes:
On 02/02/11 17:55, %u wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. -- Robert http://octarineparrot.com/
Feb 02 2011
next sibling parent reply Jacob Carlborg <doob me.com> writes:
On 2011-02-02 20:42, Robert Clipsham wrote:
 On 02/02/11 17:55, %u wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though.

Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object. -- /Jacob Carlborg
Feb 02 2011
parent reply Robert Clipsham <robert octarineparrot.com> writes:
On 02/02/11 20:00, Jacob Carlborg wrote:
 On 2011-02-02 20:42, Robert Clipsham wrote:
 On 02/02/11 17:55, %u wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though.

Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object.

If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1. -- Robert http://octarineparrot.com/
Feb 02 2011
next sibling parent reply Stanislav Blinov <stanislav.blinov gmail.com> writes:
On 02/02/2011 11:11 PM, Robert Clipsham wrote:
 On 02/02/11 20:00, Jacob Carlborg wrote:
 On 2011-02-02 20:42, Robert Clipsham wrote:
 On 02/02/11 17:55, %u wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though.

Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object.

If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1.

AFAIK, D2's TypeInfo and friends do have an interface for runtime reflection (methods offTi() and getMembers()), though a quick glance shows they're not implemented, i.e. return null all the time.
Feb 02 2011
parent Jacob Carlborg <doob me.com> writes:
On 2011-02-02 22:51, Stanislav Blinov wrote:
 On 02/02/2011 11:11 PM, Robert Clipsham wrote:
 On 02/02/11 20:00, Jacob Carlborg wrote:
 On 2011-02-02 20:42, Robert Clipsham wrote:
 On 02/02/11 17:55, %u wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though.

Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object.

If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1.

AFAIK, D2's TypeInfo and friends do have an interface for runtime reflection (methods offTi() and getMembers()), though a quick glance shows they're not implemented, i.e. return null all the time.

I think the const is incorrect as well on getMembers. -- /Jacob Carlborg
Feb 03 2011
prev sibling parent Jacob Carlborg <doob me.com> writes:
On 2011-02-02 21:11, Robert Clipsham wrote:
 On 02/02/11 20:00, Jacob Carlborg wrote:
 On 2011-02-02 20:42, Robert Clipsham wrote:
 On 02/02/11 17:55, %u wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though.

Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object.

If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1.

Same here, but you would probably need to inherit from a common base class or use a mixin. -- /Jacob Carlborg
Feb 03 2011
prev sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 2/2/11, Stanislav Blinov <stanislav.blinov gmail.com> wrote:
 AFAIK, D2's TypeInfo and friends do have an interface for runtime
 reflection (methods offTi() and getMembers()), though a quick glance
 shows they're not implemented, i.e. return null all the time.

Talk about posting this after I've spent 20 minutes trying to figure out why getMembers doesn't work!
Feb 02 2011
prev sibling next sibling parent reply "Robert Jacques" <sandford jhu.edu> writes:
On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:

 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed. Note how in the example below, only Student is manually registered; Grade is automatically registered by Variant via compile-time reflection of Student. module example; class Grade { real mark; } class Student { Grade grade; } void main(string[] args) { Variant.__register!Student; Variant grade = Object.factory("example.Grade"); grade.mark(96.6); assert(grade.mark == 96.6); } And dynamic method/field calls are handled via the __reflect(string name, Variant[] args...) method like so: grade.__reflect("mark",Variant(96.6)); assert(grade.__reflect("mark") == 96.6);
Feb 02 2011
next sibling parent reply Jacob Carlborg <doob me.com> writes:
On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:

 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed. Note how in the example below, only Student is manually registered; Grade is automatically registered by Variant via compile-time reflection of Student. module example; class Grade { real mark; } class Student { Grade grade; } void main(string[] args) { Variant.__register!Student; Variant grade = Object.factory("example.Grade"); grade.mark(96.6); assert(grade.mark == 96.6); } And dynamic method/field calls are handled via the __reflect(string name, Variant[] args...) method like so: grade.__reflect("mark",Variant(96.6)); assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant? -- /Jacob Carlborg
Feb 03 2011
next sibling parent reply Jonathan M Davis <jmdavisProg gmx.com> writes:
On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
 On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg <doob me.com> wrote:
 On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?
 
 Would something like the following be possible?
 
 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);
 
 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed. Note how in the example below, only Student is manually registered; Grade is automatically registered by Variant via compile-time reflection of Student. module example; class Grade { real mark; } class Student { Grade grade; } void main(string[] args) { Variant.__register!Student; Variant grade = Object.factory("example.Grade"); grade.mark(96.6); assert(grade.mark == 96.6); } And dynamic method/field calls are handled via the __reflect(string name, Variant[] args...) method like so: grade.__reflect("mark",Variant(96.6)); assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant?

Well, opDispatch does exactly that. __reflect, on the other hand, was designed as a quasi-backend function primarily for a) internal use (hence the double underscore), b) scripting language interfacing/implementing and c) user-extension. So efficiency was of key importance. And the reflection system is extensible, as Variant knows to call __reflect on user defined types. This makes things like prototype style objects possible. (There's even a beta implementation of a prototype object in the library) But this requires that the use __reflect methods not be templated. I'm not well versed in dynamic reflection and its use cases, so when I considered the combination of a runtime method name and compile-time argument type information, I classed it as 'rare in practice'. But if that's not the case, I'd like to know and would greatly appreciate a use case/unit test.

Most of the good examples of runtime reflection that I'm aware of require user- defined attributes. But there are libraries in Java (and presumably C#) that do stuff like allow you to mark your classes with certain attributes indicating what type of XML elements that they should be, and then another library which knows _nothing_ about your classes is able to serialize them to and from XML. Another example would be Hibernate, which does the same sort of stuff only it deals with talking to databases. Full-on runtime reflection combined with user-defined attributes can do some powerful stuff. However, I do think that runtime reflection without user-defined attributes doesn't tend to be anywhere near as useful. To really get that sort of stuff working, we'd need D to properly support both user- defined attributes and runtime reflection. Both are future possibilities but obviously aren't happening any time soon. - Jonathan M Davis
Feb 03 2011
parent reply Jacob Carlborg <doob me.com> writes:
On 2011-02-04 05:07, Jonathan M Davis wrote:
 On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
 On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg<doob me.com>  wrote:
 On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u<fghf jhgjhb.com>  wrote:
 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed. Note how in the example below, only Student is manually registered; Grade is automatically registered by Variant via compile-time reflection of Student. module example; class Grade { real mark; } class Student { Grade grade; } void main(string[] args) { Variant.__register!Student; Variant grade = Object.factory("example.Grade"); grade.mark(96.6); assert(grade.mark == 96.6); } And dynamic method/field calls are handled via the __reflect(string name, Variant[] args...) method like so: grade.__reflect("mark",Variant(96.6)); assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant?

Well, opDispatch does exactly that. __reflect, on the other hand, was designed as a quasi-backend function primarily for a) internal use (hence the double underscore), b) scripting language interfacing/implementing and c) user-extension. So efficiency was of key importance. And the reflection system is extensible, as Variant knows to call __reflect on user defined types. This makes things like prototype style objects possible. (There's even a beta implementation of a prototype object in the library) But this requires that the use __reflect methods not be templated. I'm not well versed in dynamic reflection and its use cases, so when I considered the combination of a runtime method name and compile-time argument type information, I classed it as 'rare in practice'. But if that's not the case, I'd like to know and would greatly appreciate a use case/unit test.

Most of the good examples of runtime reflection that I'm aware of require user- defined attributes. But there are libraries in Java (and presumably C#) that do stuff like allow you to mark your classes with certain attributes indicating what type of XML elements that they should be, and then another library which knows _nothing_ about your classes is able to serialize them to and from XML. Another example would be Hibernate, which does the same sort of stuff only it deals with talking to databases. Full-on runtime reflection combined with user-defined attributes can do some powerful stuff. However, I do think that runtime reflection without user-defined attributes doesn't tend to be anywhere near as useful. To really get that sort of stuff working, we'd need D to properly support both user- defined attributes and runtime reflection. Both are future possibilities but obviously aren't happening any time soon. - Jonathan M Davis

Ruby seems to get along without any kind of attributes/annotations. But on the other hand you can call a method in a class declaration and this will behave much the same as a attribute. ActiveRecord in Rails is a good example of runtime reflection. Also the Ruby XML library "builder" is a good example of runtime reflection. Maybe not acutally runtime reflection but is uses the "method_missing" method, equivalent to the "opDispatch" method in D, heavily. http://builder.rubyforge.org/ -- /Jacob Carlborg
Feb 05 2011
parent Jacob Carlborg <doob me.com> writes:
On 2011-02-08 05:54, Robert Jacques wrote:
 On Sat, 05 Feb 2011 13:14:42 -0500, Jacob Carlborg <doob me.com> wrote:
 On 2011-02-04 05:07, Jonathan M Davis wrote:

 Most of the good examples of runtime reflection that I'm aware of
 require user-
 defined attributes. But there are libraries in Java (and presumably
 C#) that do
 stuff like allow you to mark your classes with certain attributes
 indicating what
 type of XML elements that they should be, and then another library
 which knows
 _nothing_ about your classes is able to serialize them to and from
 XML. Another
 example would be Hibernate, which does the same sort of stuff only it
 deals with
 talking to databases. Full-on runtime reflection combined with
 user-defined
 attributes can do some powerful stuff. However, I do think that
 runtime reflection
 without user-defined attributes doesn't tend to be anywhere near as
 useful. To
 really get that sort of stuff working, we'd need D to properly
 support both user-
 defined attributes and runtime reflection. Both are future
 possibilities but
 obviously aren't happening any time soon.

 - Jonathan M Davis

Ruby seems to get along without any kind of attributes/annotations. But on the other hand you can call a method in a class declaration and this will behave much the same as a attribute. ActiveRecord in Rails is a good example of runtime reflection. Also the Ruby XML library "builder" is a good example of runtime reflection. Maybe not acutally runtime reflection but is uses the "method_missing" method, equivalent to the "opDispatch" method in D, heavily. http://builder.rubyforge.org/

I'm still reading up on Ruby, but so far, there are two major difference between serialization in Ruby and in D. First, Ruby isn't a systems programming language with pointers/unions/etc, so serializing all members of a class is generally okay in Ruby but isn't in D. This is the major advantage of annotations: its a fast, simple way of declaring what should and shouldn't be serialized. Second, Ruby's support for serialization creates a back door around its variable protection annotations (i.e. private,package,protected,public). Now, Ruby doesn't actually have user defined annotations as far as I can tell, but methods are always public and variables are always private. I don't believe that a reflection system should bypass encapsulation. The advantage of annotations is that they allow you to declare programmer intent and possibly separate APIs (ala const(T)) for special purposes.

Ok, lets have a look at how a serialization annotation could look like in D: class Foo { NonSerialized int x = 3; } Now the same can be done in Ruby, without any special syntax, like this: class Foo x = 3 non_serialized :x end In the Ruby example "non_serialized" would be a class/static method which recives a symbol indicating what field to skip during serialization. Actually since Ruby is a dynamically typed language I don't have declare "x". What I'm trying to say is that Ruby doesn't need a special syntax for annotations since you can in Ruby do all (most of) the things you can do with annotations but with class methods instead. In general, serialization breaks encapsulation, not just in Ruby. You can break encapsulation in D as well using .tupleof and delegates to methods. Ruby just has a different attitude. It allows you to * Call private methods using "send" * Add/remove/change methods on existing classes * Change variables declared as const It's no like Java which holds your hand all the time. It's the same with D, but in a different way. In D there's instead: * Pointers * Unions * malloc/free/delete -- /Jacob Carlborg
Feb 08 2011
prev sibling next sibling parent Andrew Wiley <debio264 gmail.com> writes:
--20cf3054a2e94c3e43049b6d3e3c
Content-Type: text/plain; charset=ISO-8859-1

On Thu, Feb 3, 2011 at 10:07 PM, Jonathan M Davis <jmdavisProg gmx.com>wrote:

 On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
 On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg <doob me.com> wrote:
 On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:
 I know is possible to create an object from its name. It's possible




 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed.



 how in the example below, only Student is manually registered; Grade



 automatically registered by Variant via compile-time reflection of
 Student.

 module example;
 class Grade { real mark; }
 class Student { Grade grade; }
 void main(string[] args) {
 Variant.__register!Student;
 Variant grade = Object.factory("example.Grade");
 grade.mark(96.6);
 assert(grade.mark == 96.6);
 }

 And dynamic method/field calls are handled via the __reflect(string
 name, Variant[] args...) method like so:

 grade.__reflect("mark",Variant(96.6));
 assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant?

Well, opDispatch does exactly that. __reflect, on the other hand, was designed as a quasi-backend function primarily for a) internal use (hence the double underscore), b) scripting language interfacing/implementing

 c) user-extension. So efficiency was of key importance. And the

 system is extensible, as Variant knows to call __reflect on user defined
 types. This makes things like prototype style objects possible. (There's
 even a beta implementation of a prototype object in the library) But this
 requires that the use __reflect methods not be templated.

 I'm not well versed in dynamic reflection and its use cases, so when I
 considered the combination of a runtime method name and compile-time
 argument type information, I classed it as 'rare in practice'. But if
 that's not the case, I'd like to know and would greatly appreciate a use
 case/unit test.

Most of the good examples of runtime reflection that I'm aware of require user- defined attributes. But there are libraries in Java (and presumably C#) that do stuff like allow you to mark your classes with certain attributes indicating what type of XML elements that they should be, and then another library which knows _nothing_ about your classes is able to serialize them to and from XML. Another example would be Hibernate, which does the same sort of stuff only it deals with talking to databases. Full-on runtime reflection combined with user-defined attributes can do some powerful stuff. However, I do think that runtime reflection without user-defined attributes doesn't tend to be anywhere near as useful. To really get that sort of stuff working, we'd need D to properly support both user- defined attributes and runtime reflection. Both are future possibilities but obviously aren't happening any time soon.

I would argue that if user-defined attributes could be implemented and tied into the existing compile time reflection system, we could reap similar benefits. One popular pattern in the serialization libraries you describe is that, for performance reasons, runtime reflection can be abandoned in favor of runtime code generation, where the same reflection system is used once to dynamically write code that can be used repeatedly. D has the advantage that such code can be written at compile time. True, runtime reflection would make this sort of thing more clean and decoupled, but even using compile time reflection, quite a bit is feasible if user-defined attributes are defined. --20cf3054a2e94c3e43049b6d3e3c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <br><br><div class=3D"gmail_quote">On Thu, Feb 3, 2011 at 10:07 PM, Jonatha= n M Davis <span dir=3D"ltr">&lt;<a href=3D"mailto:jmdavisProg gmx.com">jmda= visProg gmx.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" = style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"> <div><div></div><div class=3D"h5">On Thursday 03 February 2011 19:29:15 Rob= ert Jacques wrote:<br> &gt; On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg &lt;<a href=3D"mail= to:doob me.com">doob me.com</a>&gt; wrote:<br> &gt; &gt; On 2011-02-03 05:52, Robert Jacques wrote:<br> &gt; &gt;&gt; On Wed, 02 Feb 2011 12:55:37 -0500, %u &lt;<a href=3D"mailto:= fghf jhgjhb.com">fghf jhgjhb.com</a>&gt; wrote:<br> &gt; &gt;&gt;&gt; I know is possible to create an object from its name. It&= #39;s possible to<br> &gt; &gt;&gt;&gt; call a method from that object if the name is only known = at runtime?<br> &gt; &gt;&gt;&gt;<br> &gt; &gt;&gt;&gt; Would something like the following be possible?<br> &gt; &gt;&gt;&gt;<br> &gt; &gt;&gt;&gt; string classname, methodname;<br> &gt; &gt;&gt;&gt; // Ask the user for class and method.<br> &gt; &gt;&gt;&gt; auto obj =3D Object.factory(classname);<br> &gt; &gt;&gt;&gt; invoke(methodname, obj, param1, param2);<br> &gt; &gt;&gt;&gt;<br> &gt; &gt;&gt;&gt; Thanks<br> &gt; &gt;&gt;<br> &gt; &gt;&gt; I&#39;ve been working on an update to std.variant, which incl= udes a<br> &gt; &gt;&gt; compile-time reflection to runtime-reflection system. (See<br=

ml/" target=3D"_blank">https://jshare.johnshopkins.edu/rjacque2/public_html= /</a>) From the docs:<br> &gt; &gt;&gt;<br> &gt; &gt;&gt; Manually registers a class with Variant&#39;s runtime-reflect= ion system.<br> &gt; &gt;&gt; Note that Variant automatically registers any types it is exp= osed. Note<br> &gt; &gt;&gt; how in the example below, only Student is manually registered= ; Grade is<br> &gt; &gt;&gt; automatically registered by Variant via compile-time reflecti= on of<br> &gt; &gt;&gt; Student.<br> &gt; &gt;&gt;<br> &gt; &gt;&gt; module example;<br> &gt; &gt;&gt; class Grade { real mark; }<br> &gt; &gt;&gt; class Student { Grade grade; }<br> &gt; &gt;&gt; void main(string[] args) {<br> &gt; &gt;&gt; Variant.__register!Student;<br> &gt; &gt;&gt; Variant grade =3D Object.factory(&quot;example.Grade&quot;);<= br> &gt; &gt;&gt; grade.mark(96.6);<br> &gt; &gt;&gt; assert(grade.mark =3D=3D 96.6);<br> &gt; &gt;&gt; }<br> &gt; &gt;&gt;<br> &gt; &gt;&gt; And dynamic method/field calls are handled via the __reflect(= string<br> &gt; &gt;&gt; name, Variant[] args...) method like so:<br> &gt; &gt;&gt;<br> &gt; &gt;&gt; grade.__reflect(&quot;mark&quot;,Variant(96.6));<br> &gt; &gt;&gt; assert(grade.__reflect(&quot;mark&quot;) =3D=3D 96.6);<br> &gt; &gt;<br> &gt; &gt; Why would you need to pass in Variants in __reflect? Why not just= make<br> &gt; &gt; it a variadic method and automatically convert to Variant?<br> &gt;<br> &gt; Well, opDispatch does exactly that. __reflect, on the other hand, was<= br> &gt; designed as a quasi-backend function primarily for a) internal use (he= nce<br> &gt; the double underscore), b) scripting language interfacing/implementing= and<br> &gt; c) user-extension. So efficiency was of key importance. And the reflec= tion<br> &gt; system is extensible, as Variant knows to call __reflect on user defin= ed<br> &gt; types. This makes things like prototype style objects possible. (There= &#39;s<br> &gt; even a beta implementation of a prototype object in the library) But t= his<br> &gt; requires that the use __reflect methods not be templated.<br> &gt;<br> &gt; I&#39;m not well versed in dynamic reflection and its use cases, so wh= en I<br> &gt; considered the combination of a runtime method name and compile-time<b= r> &gt; argument type information, I classed it as &#39;rare in practice&#39;.= But if<br> &gt; that&#39;s not the case, I&#39;d like to know and would greatly apprec= iate a use<br> &gt; case/unit test.<br> <br> </div></div>Most of the good examples of runtime reflection that I&#39;m aw= are of require user-<br> defined attributes. But there are libraries in Java (and presumably C#) tha= t do<br> stuff like allow you to mark your classes with certain attributes indicatin= g what<br> type of XML elements that they should be, and then another library which kn= ows<br> _nothing_ about your classes is able to serialize them to and from XML. Ano= ther<br> example would be Hibernate, which does the same sort of stuff only it deals= with<br> talking to databases. Full-on runtime reflection combined with user-defined= <br> attributes can do some powerful stuff. However, I do think that runtime ref= lection<br> without user-defined attributes doesn&#39;t tend to be anywhere near as use= ful. To<br> really get that sort of stuff working, we&#39;d need D to properly support = both user-<br> defined attributes and runtime reflection. Both are future possibilities bu= t<br> obviously aren&#39;t happening any time soon.</blockquote><div><br></div><d= iv>I would argue that if user-defined attributes could be implemented and t= ied into the existing compile time reflection system, we could reap similar= benefits. One popular pattern in the serialization libraries you describe = is that, for performance reasons, runtime reflection can be abandoned in fa= vor of runtime code generation, where the same reflection system is used on= ce to dynamically write code that can be used repeatedly. D has the advanta= ge that such code can be written at compile time.</div> <div>True, runtime reflection would make this sort of thing more clean and = decoupled, but even using compile time reflection, quite a bit is feasible = if user-defined attributes are defined.</div></div><br> --20cf3054a2e94c3e43049b6d3e3c--
Feb 03 2011
prev sibling next sibling parent reply Jacob Carlborg <doob me.com> writes:
On 2011-02-04 04:29, Robert Jacques wrote:
 On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg <doob me.com> wrote:

 On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:

 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed. Note how in the example below, only Student is manually registered; Grade is automatically registered by Variant via compile-time reflection of Student. module example; class Grade { real mark; } class Student { Grade grade; } void main(string[] args) { Variant.__register!Student; Variant grade = Object.factory("example.Grade"); grade.mark(96.6); assert(grade.mark == 96.6); } And dynamic method/field calls are handled via the __reflect(string name, Variant[] args...) method like so: grade.__reflect("mark",Variant(96.6)); assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant?

Well, opDispatch does exactly that. __reflect, on the other hand, was designed as a quasi-backend function primarily for a) internal use (hence the double underscore), b) scripting language interfacing/implementing and c) user-extension. So efficiency was of key importance. And the reflection system is extensible, as Variant knows to call __reflect on user defined types. This makes things like prototype style objects possible. (There's even a beta implementation of a prototype object in the library) But this requires that the use __reflect methods not be templated. I'm not well versed in dynamic reflection and its use cases, so when I considered the combination of a runtime method name and compile-time argument type information, I classed it as 'rare in practice'. But if that's not the case, I'd like to know and would greatly appreciate a use case/unit test.

I recommend looking at Ruby, it has very good support for runtime reflection. ActiveRecord in Rails is hevaly based on runtime reflection. For example, given the following Ruby class: class Post < ActiveRecord::Base end The class "Post" maps to the database table "posts", no configuration is necessary. Then you can use the column names in the table as fields to set and get data, like this: post = Post.new post.title = "some title" post.body = "the body" post.save # will update the database All this is done using runtime reflection. Then you can query the database, also using runtime reflection: Post.find_by_name_and_body("some title", "the body") Will find the first row where "title" and "body" matches the given values. -- /Jacob Carlborg
Feb 04 2011
next sibling parent reply Adam Ruppe <destructionator gmail.com> writes:
Jacob Carlborg wrote:
 The class "Post" maps to the database table "posts", no configuration is
 necessary. Then you can use the column names in the table as fields to
 set and get data, like this:

 post = Post.new
 post.title = "some title"
 post.body = "the body"
 post.save # will update the database

Note that you can do this kind of thing with D's compile time reflection and CTFE as well. That particular example works in my own DataObject class (except I called it "commitChanges" instead of "save"). Some of the stuff is just dynamic; just sugar around a string[string]. Most my own use of "runtime reflection" is just having some CTFE go through and put the compile time info into those strings which are used at runtime. I do that for calling functions by name too, but mine does rely upon some static info that probably isn't available to the OP. For example for both, my new newsreader does both: http://arsdnet.net/d-web-site/nntp/get-message That screen is automatically generated by this prototype: Post getMessage(string newsgroup, string messageId) { The name of the function and arguments in the URL are pulled from that single line of code. It uses the types of the arguments to automatically generate an appropriate form. The way I did it was to put all the public functions in a static struct. Then, I mixin a template (called FancyMain!(methodStruct)) which scans the struct and generates the needed hashmaps and delegates to call its methods by name. http://arsdnet.net/d-web-site/arsd/web.d That code is very ugly... but look at the prepareReflection and generateWrapper functions.
Feb 04 2011
parent Jacob Carlborg <doob me.com> writes:
On 2011-02-04 17:17, Adam Ruppe wrote:
 Jacob Carlborg wrote:
 The class "Post" maps to the database table "posts", no configuration is
 necessary. Then you can use the column names in the table as fields to
 set and get data, like this:

 post = Post.new
 post.title = "some title"
 post.body = "the body"
 post.save # will update the database

Note that you can do this kind of thing with D's compile time reflection and CTFE as well. That particular example works in my own DataObject class (except I called it "commitChanges" instead of "save").

Yeah, I tried to do the same. But in this case the static type system was kind of in the way of what I wanted to do. This is so much easier with a dynamic type system. -- /Jacob Carlborg
Feb 05 2011
prev sibling parent Jacob Carlborg <doob me.com> writes:
On 2011-02-04 20:03, spir wrote:
 On 02/04/2011 04:33 PM, Jacob Carlborg wrote:
 I recommend looking at Ruby, it has very good support for runtime
 reflection.
 ActiveRecord in Rails is hevaly based on runtime reflection. For
 example, given
 the following Ruby class:

 class Post < ActiveRecord::Base
 end

 The class "Post" maps to the database table "posts", no configuration is
 necessary. Then you can use the column names in the table as fields to
 set and
 get data, like this:

 post = Post.new
 post.title = "some title"
 post.body = "the body"
 post.save # will update the database

 All this is done using runtime reflection. Then you can query the
 database,
 also using runtime reflection:

 Post.find_by_name_and_body("some title", "the body")

 Will find the first row where "title" and "body" matches the given
 values.

FWIW, python example of "Calling method by name" (using no exotic feature): class C: def __init__(self, x): self.x = x def write (self, thing): print "%s == %s ? %s" \ %(self.x,thing, self.x==thing) def runMethodWithArgs (object, name, *args): method = getattr(object, name) method(*args) c= C(1.11) runMethodWithArgs(c, "write", 2.22) # --> 1.11 == 2.22 ? False (Explanations if needed.) Denis

Actually I never showed how to do "call by name" in Ruby, just how it can be used. Ruby has "built in" (not in the language but in the Object class) support for this: p Object.new.send(:to_s) # :to_s is a symbol, basically an immutable lightweight string The above will print something like: "#<Object:0x101279bb8>" To implement the "find_by" methods used in my previous examples you implement the "method_missing" method: class Foo def method_missing (method, *args, &block) p method, args end end Foo.new.bar 3, 4 Will print: :bar [3, 4] -- /Jacob Carlborg
Feb 06 2011
prev sibling parent "Robert Jacques" <sandford jhu.edu> writes:
On Sat, 05 Feb 2011 13:14:42 -0500, Jacob Carlborg <doob me.com> wrote:
 On 2011-02-04 05:07, Jonathan M Davis wrote:

 Most of the good examples of runtime reflection that I'm aware of  
 require user-
 defined attributes. But there are libraries in Java (and presumably C#)  
 that do
 stuff like allow you to mark your classes with certain attributes  
 indicating what
 type of XML elements that they should be, and then another library  
 which knows
 _nothing_ about your classes is able to serialize them to and from XML.  
 Another
 example would be Hibernate, which does the same sort of stuff only it  
 deals with
 talking to databases. Full-on runtime reflection combined with  
 user-defined
 attributes can do some powerful stuff. However, I do think that runtime  
 reflection
 without user-defined attributes doesn't tend to be anywhere near as  
 useful. To
 really get that sort of stuff working, we'd need D to properly support  
 both user-
 defined attributes and runtime reflection. Both are future  
 possibilities but
 obviously aren't happening any time soon.

 - Jonathan M Davis

Ruby seems to get along without any kind of attributes/annotations. But on the other hand you can call a method in a class declaration and this will behave much the same as a attribute. ActiveRecord in Rails is a good example of runtime reflection. Also the Ruby XML library "builder" is a good example of runtime reflection. Maybe not acutally runtime reflection but is uses the "method_missing" method, equivalent to the "opDispatch" method in D, heavily. http://builder.rubyforge.org/

I'm still reading up on Ruby, but so far, there are two major difference between serialization in Ruby and in D. First, Ruby isn't a systems programming language with pointers/unions/etc, so serializing all members of a class is generally okay in Ruby but isn't in D. This is the major advantage of annotations: its a fast, simple way of declaring what should and shouldn't be serialized. Second, Ruby's support for serialization creates a back door around its variable protection annotations (i.e. private,package,protected,public). Now, Ruby doesn't actually have user defined annotations as far as I can tell, but methods are always public and variables are always private. I don't believe that a reflection system should bypass encapsulation. The advantage of annotations is that they allow you to declare programmer intent and possibly separate APIs (ala const(T)) for special purposes.
Feb 07 2011
prev sibling parent "Robert Jacques" <sandford jhu.edu> writes:
On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg <doob me.com> wrote:

 On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:

 I know is possible to create an object from its name. It's possible to
 call a method from that object if the name is only known at runtime?

 Would something like the following be possible?

 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);

 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed. Note how in the example below, only Student is manually registered; Grade is automatically registered by Variant via compile-time reflection of Student. module example; class Grade { real mark; } class Student { Grade grade; } void main(string[] args) { Variant.__register!Student; Variant grade = Object.factory("example.Grade"); grade.mark(96.6); assert(grade.mark == 96.6); } And dynamic method/field calls are handled via the __reflect(string name, Variant[] args...) method like so: grade.__reflect("mark",Variant(96.6)); assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant?

Well, opDispatch does exactly that. __reflect, on the other hand, was designed as a quasi-backend function primarily for a) internal use (hence the double underscore), b) scripting language interfacing/implementing and c) user-extension. So efficiency was of key importance. And the reflection system is extensible, as Variant knows to call __reflect on user defined types. This makes things like prototype style objects possible. (There's even a beta implementation of a prototype object in the library) But this requires that the use __reflect methods not be templated. I'm not well versed in dynamic reflection and its use cases, so when I considered the combination of a runtime method name and compile-time argument type information, I classed it as 'rare in practice'. But if that's not the case, I'd like to know and would greatly appreciate a use case/unit test.
Feb 03 2011
prev sibling next sibling parent Stanislav Blinov <blinov loniir.ru> writes:
03.02.2011 12:54, Jacob Carlborg пишет:
 On 2011-02-02 22:51, Stanislav Blinov wrote:
 AFAIK, D2's TypeInfo and friends do have an interface for runtime
 reflection (methods offTi() and getMembers()), though a quick glance
 shows they're not implemented, i.e. return null all the time.

I think the const is incorrect as well on getMembers.

const-correct, as is the case for Object and other Object-related classes.
Feb 03 2011
prev sibling next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On Thursday 03 February 2011 20:23:25 Andrew Wiley wrote:
 On Thu, Feb 3, 2011 at 10:07 PM, Jonathan M Davis <jmdavisProg gmx.com>wrote:
 On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
 On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg <doob me.com> wrote:
 On 2011-02-03 05:52, Robert Jacques wrote:
 On Wed, 02 Feb 2011 12:55:37 -0500, %u <fghf jhgjhb.com> wrote:
 I know is possible to create an object from its name. It's possible




to
 call a method from that object if the name is only known at
 runtime?
 
 Would something like the following be possible?
 
 string classname, methodname;
 // Ask the user for class and method.
 auto obj = Object.factory(classname);
 invoke(methodname, obj, param1, param2);
 
 Thanks

I've been working on an update to std.variant, which includes a compile-time reflection to runtime-reflection system. (See https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs: Manually registers a class with Variant's runtime-reflection system. Note that Variant automatically registers any types it is exposed.



Note
 how in the example below, only Student is manually registered; Grade



is
 automatically registered by Variant via compile-time reflection of
 Student.
 
 module example;
 class Grade { real mark; }
 class Student { Grade grade; }
 void main(string[] args) {
 Variant.__register!Student;
 Variant grade = Object.factory("example.Grade");
 grade.mark(96.6);
 assert(grade.mark == 96.6);
 }
 
 And dynamic method/field calls are handled via the __reflect(string
 name, Variant[] args...) method like so:
 
 grade.__reflect("mark",Variant(96.6));
 assert(grade.__reflect("mark") == 96.6);

Why would you need to pass in Variants in __reflect? Why not just make it a variadic method and automatically convert to Variant?

Well, opDispatch does exactly that. __reflect, on the other hand, was designed as a quasi-backend function primarily for a) internal use (hence the double underscore), b) scripting language interfacing/implementing

and
 c) user-extension. So efficiency was of key importance. And the

reflection
 system is extensible, as Variant knows to call __reflect on user
 defined types. This makes things like prototype style objects
 possible. (There's even a beta implementation of a prototype object in
 the library) But this requires that the use __reflect methods not be
 templated.
 
 I'm not well versed in dynamic reflection and its use cases, so when I
 considered the combination of a runtime method name and compile-time
 argument type information, I classed it as 'rare in practice'. But if
 that's not the case, I'd like to know and would greatly appreciate a
 use case/unit test.

Most of the good examples of runtime reflection that I'm aware of require user- defined attributes. But there are libraries in Java (and presumably C#) that do stuff like allow you to mark your classes with certain attributes indicating what type of XML elements that they should be, and then another library which knows _nothing_ about your classes is able to serialize them to and from XML. Another example would be Hibernate, which does the same sort of stuff only it deals with talking to databases. Full-on runtime reflection combined with user-defined attributes can do some powerful stuff. However, I do think that runtime reflection without user-defined attributes doesn't tend to be anywhere near as useful. To really get that sort of stuff working, we'd need D to properly support both user- defined attributes and runtime reflection. Both are future possibilities but obviously aren't happening any time soon.

I would argue that if user-defined attributes could be implemented and tied into the existing compile time reflection system, we could reap similar benefits. One popular pattern in the serialization libraries you describe is that, for performance reasons, runtime reflection can be abandoned in favor of runtime code generation, where the same reflection system is used once to dynamically write code that can be used repeatedly. D has the advantage that such code can be written at compile time. True, runtime reflection would make this sort of thing more clean and decoupled, but even using compile time reflection, quite a bit is feasible if user-defined attributes are defined.

I've never really sat down to try and figure out how well compile time reflection would work for that sort of thing (particularly since D is the only language I know of with any kind of compile time reflection), but since we don't have user- defined attributes yet, we can't do it regardless. If we could pull it off with compile time reflection, then maybe we wouldn't really need runtime reflection. I don't know. But we'll need user-defined attributes before we can do anything like that, and exactly what the limitations and possibilities are may not be particularly clear before we can actually play around with user-defined attributes and compile time reflection. You may be right though, and runtime wouldn't be needed to do some of the cooler things that you can do with runtime reflection in languages like Java. Regardless, I've found compile time reflection to be far more helpful in my everday code than I've ever found runtime reflection to be. - Jonathan M Davis
Feb 03 2011
prev sibling parent spir <denis.spir gmail.com> writes:
On 02/04/2011 04:33 PM, Jacob Carlborg wrote:
 On 2011-02-04 04:29, Robert Jacques wrote:
 On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg <doob me.com> wrote:


 Well, opDispatch does exactly that. __reflect, on the other hand, was
 designed as a quasi-backend function primarily for a) internal use
 (hence the double underscore), b) scripting language
 interfacing/implementing and c) user-extension. So efficiency was of key
 importance. And the reflection system is extensible, as Variant knows to
 call __reflect on user defined types. This makes things like prototype
 style objects possible. (There's even a beta implementation of a
 prototype object in the library) But this requires that the use
 __reflect methods not be templated.

 I'm not well versed in dynamic reflection and its use cases, so when I
 considered the combination of a runtime method name and compile-time
 argument type information, I classed it as 'rare in practice'. But if
 that's not the case, I'd like to know and would greatly appreciate a use
 case/unit test.

I recommend looking at Ruby, it has very good support for runtime reflection. ActiveRecord in Rails is hevaly based on runtime reflection. For example, given the following Ruby class: class Post < ActiveRecord::Base end The class "Post" maps to the database table "posts", no configuration is necessary. Then you can use the column names in the table as fields to set and get data, like this: post = Post.new post.title = "some title" post.body = "the body" post.save # will update the database All this is done using runtime reflection. Then you can query the database, also using runtime reflection: Post.find_by_name_and_body("some title", "the body") Will find the first row where "title" and "body" matches the given values.

FWIW, python example of "Calling method by name" (using no exotic feature): class C: def __init__(self, x): self.x = x def write (self, thing): print "%s == %s ? %s" \ %(self.x,thing, self.x==thing) def runMethodWithArgs (object, name, *args): method = getattr(object, name) method(*args) c= C(1.11) runMethodWithArgs(c, "write", 2.22) # --> 1.11 == 2.22 ? False (Explanations if needed.) Denis -- _________________ vita es estrany spir.wikidot.com
Feb 04 2011