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digitalmars.D.learn - Get identifier of "this"

reply "Andre" <andre s-e-a-p.de> writes:
Hi,

assuming I have following constuct:

public class Bank{
    public enum test()
    {
      return "writeln(\""~__traits(identfier, this)~"\");";
    }
}

public static void main(){
    Bank b = new Bank;
    mixin(b.test());
}

During compile time, following code should be generated:
writeln("b");

Is this possible? For the demo coding I receive the error, that
"this"
has no identifier.

Kind regards
Andre
Sep 17 2012
next sibling parent reply Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 9/17/12, Andre <andre s-e-a-p.de> wrote:

 Get identifier of "this"


You can't really get that info at runtime, a class object isn't bound
to a name, 'this' has no identifier. Symbols (like variables) have
identifiers, not objects.


 public class Bank{


Unnecessary, declarations are public by default.


     public enum test()


'enum' has no meaning in a return type. Either it's 'auto' which
infers the return type from the function body, or it's a specific type
like 'string' (or void if no return type).


     {
       return "writeln(\""~__traits(identfier, this)~"\");";


typo: identifier, not identfier


     }
 }



 public static void main(){


public and static have no meaning here.


 During compile time, following code should be generated:
 writeln("b");


It's not possible to mixin a string at compile-time from a string
returned from a method of an object which is instantiated at runtime.
If you want the identifier of the variable then you don't have to deal
with the 'this' reference at all, e.g.:

 property string test(alias symb)()
{
    return "writeln(\"" ~ __traits(identifier, symb) ~ "\");";
}

class Bank { }

void main()
{
    Bank b = new Bank;
    mixin(test!b);
}

Your original sample does cause a compiler ICE but I don't know if
it's worth filing since the code was invalid.
Sep 17 2012
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Mon, 17 Sep 2012 14:01:35 -0400, Andrej Mitrovic  
<andrej.mitrovich gmail.com> wrote:


 Your original sample does cause a compiler ICE but I don't know if
 it's worth filing since the code was invalid.


Please file, ICE should never occur.

-Steve
Sep 17 2012
parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 9/17/12, Steven Schveighoffer <schveiguy yahoo.com> wrote:

 Please file, ICE should never occur.


You're bound to find a small million of these when it comes to typos
in templates. :)
http://d.puremagic.com/issues/show_bug.cgi?id=8679
Sep 17 2012
prev sibling parent "Andre" <andre s-e-a-p.de> writes:
On Monday, 17 September 2012 at 18:01:02 UTC, Andrej Mitrovic
wrote:

 On 9/17/12, Andre <andre s-e-a-p.de> wrote:

 Get identifier of "this"


 You can't really get that info at runtime, a class object isn't 
 bound
 to a name, 'this' has no identifier. Symbols (like variables) 
 have
 identifiers, not objects.


...

Hi Andrej,

thanks a lot for the working sample coding,
this helps me.

Kind regards
Andre
Sep 17 2012
prev sibling parent "Jonathan M Davis" <jmdavisProg gmx.com> writes:
On Monday, September 17, 2012 19:43:24 Andre wrote:

 Hi,
 
 assuming I have following constuct:
 
 public class Bank{
 public enum test()
 {
 return "writeln(\""~__traits(identfier, this)~"\");";
 }
 }
 
 public static void main(){
 Bank b = new Bank;
 mixin(b.test());
 }
 
 During compile time, following code should be generated:
 writeln("b");
 
 Is this possible? For the demo coding I receive the error, that
 "this"
 has no identifier.


No. It's not possible. __traits is a compile-time construct, and Bank's 
definition knows nothing about any variables of type Bank declared elsewhere. 
Heck, the code for Bank could be compiled months before the code with b in it 
is even written (and then has the code with Bank linked to it when it's 
compiled). So no, it can't know about b, and what you're trying to do won't 
work.

- Jonathan M Davis
Sep 17 2012