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digitalmars.D.announce - Another event handling module

reply "John C" <johnch_atms hotmail.com> writes:
A few classes for multicast event handling have been previously released, 
and here's another. I think this one's unique in that it allows you to use 
both delegates and function pointers (although I may be wrong).

Read more or download it here:
http://www.paperocean.org/cirrus.core.events.html

If you find any bugs, please let me know.

BTW: I've added various ways of chaining together delegates/function 
(opAddAssign/opSubAssign, opCatAssign, add/remove method calls). This way 
you can use the one you prefer.

John. 
Sep 10 2005
parent reply Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
John C wrote:
 A few classes for multicast event handling have been previously released, 
 and here's another. I think this one's unique in that it allows you to use 
 both delegates and function pointers (although I may be wrong).

dcouple at dsource has them too :-) What do you do when a recipient gets deleted? Bastiaan.
Sep 11 2005
parent reply "John C" <johnch_atms hotmail.com> writes:
"Bastiaan Veelo" <Bastiaan.N.Veelo ntnu.no> wrote in message 
news:dg1e0u$2ihm$1 digitaldaemon.com...
 John C wrote:
 A few classes for multicast event handling have been previously released, 
 and here's another. I think this one's unique in that it allows you to 
 use both delegates and function pointers (although I may be wrong).

dcouple at dsource has them too :-) What do you do when a recipient gets deleted?

Good question ... my test program crashes and there doesn't appear to be a way to check if the delegate still exists - testing for null doesn't work. Also, I was unable to catch any exceptions. Ideas? As a workaround, you can call 'remove' to break the connection in the receiver's destructor. But I'm not sure how this can be done when a function literal is attached, though. I've noticed that Ben Hinkle's MultiDelegate exhibits the same problem. I've not tested dcouple. Shouldn't the compiler null out delegates that reference nonexistent methods?
Sep 11 2005
next sibling parent Sean Kelly <sean f4.ca> writes:
In article <dg1r4v$2tcj$1 digitaldaemon.com>, John C says...
"Bastiaan Veelo" <Bastiaan.N.Veelo ntnu.no> wrote in message 
news:dg1e0u$2ihm$1 digitaldaemon.com...
 John C wrote:
 A few classes for multicast event handling have been previously released, 
 and here's another. I think this one's unique in that it allows you to 
 use both delegates and function pointers (although I may be wrong).

dcouple at dsource has them too :-) What do you do when a recipient gets deleted?

Good question ... my test program crashes and there doesn't appear to be a way to check if the delegate still exists - testing for null doesn't work. Also, I was unable to catch any exceptions. Ideas?

I'm not sure if this applies directly, but I use proxy classes for this purpose in C++. The basic idea is something like this: # class Proxy(Dest) { # this() {} # this( Dest d ) { attach( d ); } # void attach( Dest d ) { m_dest = d; } # void detach() { m_dest = null; } # void opCall() { if( m_dest ) m_dest(); } # private Dest m_dest; # } # # class C { # ~this() { # foreach( Proxy!(C) p; m_proxies ) # p.detach(); # } # void doSomething() { # Proxy!(C) p = new Proxy!(C)( this ); # // pass proxy to callback # m_proxies ~= p; # } # private Proxy!(C)[] m_proxies; # }
As a workaround, you can call 'remove' to break the connection in the 
receiver's destructor.

Sounds like you're doing something like the above.
But I'm not sure how this can be done when a function 
literal is attached, though.

A delegate you mean? There's not much you can do aside from perhaps putting the call in a try{}catch(Object){} block, as I think this will trap the access violation if the referenced object has been destroyed.
I've noticed that Ben Hinkle's MultiDelegate exhibits the same problem. I've 
not tested dcouple.

Shouldn't the compiler null out delegates that reference nonexistent 
methods?

If so then it may as well do the same for references to objects that have been cleaned up. I think the issue is that this is simply too expensive to be worthwhile in most cases. Sean
Sep 11 2005
prev sibling next sibling parent reply "Ben Hinkle" <bhinkle mathworks.com> writes:
"John C" <johnch_atms hotmail.com> wrote in message 
news:dg1r4v$2tcj$1 digitaldaemon.com...
 "Bastiaan Veelo" <Bastiaan.N.Veelo ntnu.no> wrote in message 
 news:dg1e0u$2ihm$1 digitaldaemon.com...
 John C wrote:
 A few classes for multicast event handling have been previously 
 released, and here's another. I think this one's unique in that it 
 allows you to use both delegates and function pointers (although I may 
 be wrong).

dcouple at dsource has them too :-) What do you do when a recipient gets deleted?

Good question ... my test program crashes and there doesn't appear to be a way to check if the delegate still exists - testing for null doesn't work. Also, I was unable to catch any exceptions. Ideas? As a workaround, you can call 'remove' to break the connection in the receiver's destructor. But I'm not sure how this can be done when a function literal is attached, though. I've noticed that Ben Hinkle's MultiDelegate exhibits the same problem. I've not tested dcouple.

Correct. When a programmer deletes an object by hand it is a promise that no other live references exist. Violating that promise results in crashes.
 Shouldn't the compiler null out delegates that reference nonexistent 
 methods?

Sep 11 2005
parent "John C" <johnch_atms hotmail.com> writes:
"Ben Hinkle" <bhinkle mathworks.com> wrote in message 
news:dg24mg$2r4$1 digitaldaemon.com...
 "John C" <johnch_atms hotmail.com> wrote in message 
 news:dg1r4v$2tcj$1 digitaldaemon.com...
 "Bastiaan Veelo" <Bastiaan.N.Veelo ntnu.no> wrote in message 
 news:dg1e0u$2ihm$1 digitaldaemon.com...
 John C wrote:
 A few classes for multicast event handling have been previously 
 released, and here's another. I think this one's unique in that it 
 allows you to use both delegates and function pointers (although I may 
 be wrong).

dcouple at dsource has them too :-) What do you do when a recipient gets deleted?

Good question ... my test program crashes and there doesn't appear to be a way to check if the delegate still exists - testing for null doesn't work. Also, I was unable to catch any exceptions. Ideas? As a workaround, you can call 'remove' to break the connection in the receiver's destructor. But I'm not sure how this can be done when a function literal is attached, though. I've noticed that Ben Hinkle's MultiDelegate exhibits the same problem. I've not tested dcouple.

Correct. When a programmer deletes an object by hand it is a promise that no other live references exist. Violating that promise results in crashes.

Sounds like a fair rule. After all, if you're explictly calling delete you'll probably want to ensure everything else is cleaned up too.
 Shouldn't the compiler null out delegates that reference nonexistent 
 methods?


Sep 11 2005
prev sibling parent reply Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
John C wrote:

What do you do when a recipient gets deleted?

Good question ... my test program crashes and there doesn't appear to be a way to check if the delegate still exists - testing for null doesn't work. Also, I was unable to catch any exceptions. Ideas? As a workaround, you can call 'remove' to break the connection in the receiver's destructor. But I'm not sure how this can be done when a function literal is attached, though. I've noticed that Ben Hinkle's MultiDelegate exhibits the same problem. I've not tested dcouple.

Dcouple solves this with Slot objects and managing code. I am ioning out some segfaults in version 0.3, but 0.2 should work.
 Shouldn't the compiler null out delegates that reference nonexistent 
 methods? 

That would be nice, but how would the compiler know? There is a concept called weak references, that has been brought up a couple of times in this context. See the post "Resources" on the dcouple forum at dsource. Bastiaan.
Sep 12 2005
parent reply Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
Bastiaan Veelo wrote:

 Dcouple solves this with Slot objects and managing code.

Version 0.3 (currently in the svn trunk) works per today (http://svn.dsource.org/projects/dcouple/trunk/managed/dcouple/). The dcouple version of Ben's example from multidg.d is given below #import dcouple.connect; #import dcouple.release; #import dcouple.signalslot; # #class Foo : SignalSlotManager #{ # mixin SignalSlotManagement; # # Signal!(int) valueChanged; # Slot!(int) changeValue; # # private int val; # # this() # { # valueChanged = new Signal!(int)(this); # changeValue = new Slot!(int)(this, &value); # } # # ~this() # { # deleteSignals(); # deleteSlots(); # } # # int value() # { # return val; # } # # void value(int v) # { # if (val != v) { # val = v; # valueChanged.emit(v); # } # } #} # #import std.stdio; #int main() { # writefln("Compiled with ", dcoupleVersion() ); # Foo a = new Foo; # Foo b = new Foo; # connect(a.valueChanged, b.changeValue); # writefln(a.value," ",b.value); # b.value = 11; # writefln(a.value," ",b.value); # a.value = 79; # writefln(a.value," ",b.value); # delete b; // Note delete! # a.value = 100; # writefln(a.value); # return 0; #} (also available here http://svn.dsource.org/projects/dcouple/trunk/managed/examples/delete_example.d) output is Compiled with dcouple version 0.3, copyright 2004, 2005 Bastiaan Veelo. 0 0 0 11 79 79 100 So dcouple lets you tie together objects, and handle them any way you like regardless what ties exist. If you delete an object, existing ties clean themselves up. Bastiaan.
Sep 13 2005
next sibling parent reply "Ben Hinkle" <bhinkle mathworks.com> writes:
 #  ~this()
 #  {
 #    deleteSignals();
 #    deleteSlots();
 #  }

Does deleteSignals and deleteSlots reference other GC-managed objects or arrays? If so then you'll get random seg-v's during a GC. Objects are collected in random order and so the other objects might be gone by the time ~this runs. The details (as they are) are in http://www.digitalmars.com/d/class.html#destructors
Sep 13 2005
parent reply Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
Ben Hinkle wrote:
#  ~this()
#  {
#    deleteSignals();
#    deleteSlots();
#  }

Does deleteSignals and deleteSlots reference other GC-managed objects or arrays?

Yes, but only to objects (Signals and Slots) that know about each other and about their managers (the ones calling deleteSignals and/or deleteSlots). In their destructor they deregister themselves with these referencing objects. So at the time of destruction, only references exist to objects that have not been destructed yet. Therefore, the order of destruction does not matter. Bastiaan.
Sep 14 2005
next sibling parent reply "Ben Hinkle" <ben.hinkle gmail.com> writes:
"Bastiaan Veelo" <Bastiaan.N.Veelo ntnu.no> wrote in message 
news:dg8nsc$f9l$1 digitaldaemon.com...
 Ben Hinkle wrote:
#  ~this()
#  {
#    deleteSignals();
#    deleteSlots();
#  }

Does deleteSignals and deleteSlots reference other GC-managed objects or arrays?

Yes, but only to objects (Signals and Slots) that know about each other and about their managers (the ones calling deleteSignals and/or deleteSlots). In their destructor they deregister themselves with these referencing objects. So at the time of destruction, only references exist to objects that have not been destructed yet. Therefore, the order of destruction does not matter.

Ok, though note the dynamic array used to store the data is also GC-managed and has no destructor.
 Bastiaan. 

Sep 14 2005
parent reply Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
Ben Hinkle wrote:

 Ok, though note the dynamic array used to store the data is also GC-managed 
 and has no destructor.

Hm. Thanks for pointing that out. I have not been bitten by that fact yet, could it be that objects do get collected before arrays in the current implementation of the garbage collector? What do you think would be the best defence, a linked list using malloc and free? Dcouple is kind of a study for me, I am not sure yet whether it is better/nicer to explicitly delete an object or to disconnect all its connections (e.g. by means of a "discard" method) and let the GC take care of it. I am mainly thinking GUI programming here.
Sep 15 2005
parent =?utf-8?B?RGF3aWQgQ2nEmcW8YXJraWV3aWN6?= <araelx gmail.com> writes:
On Thu, 15 Sep 2005 17:12:06 +0200, Bastiaan Veelo  
<Bastiaan.N.Veelo ntnu.no> wrote:

 Dcouple is kind of a study for me, I am not sure yet whether it is  
 better/nicer to explicitly delete an object or to disconnect all its  
 connections (e.g. by means of a "discard" method) and let the GC take  
 care of it. I am mainly thinking GUI programming here.

Very good question. I often consider this problem by myself. "Dereference and forget" vs. "explicity delete". Any thoughts about this matter, anyone? -- Dawid Ciężarkiewicz
Sep 15 2005
prev sibling parent reply "Ben Hinkle" <bhinkle mathworks.com> writes:
"Bastiaan Veelo" <Bastiaan.N.Veelo ntnu.no> wrote in message 
news:dg8nsc$f9l$1 digitaldaemon.com...
 Ben Hinkle wrote:
#  ~this()
#  {
#    deleteSignals();
#    deleteSlots();
#  }

Does deleteSignals and deleteSlots reference other GC-managed objects or arrays?

Yes, but only to objects (Signals and Slots) that know about each other and about their managers (the ones calling deleteSignals and/or deleteSlots). In their destructor they deregister themselves with these referencing objects. So at the time of destruction, only references exist to objects that have not been destructed yet. Therefore, the order of destruction does not matter. Bastiaan.

I should add that if all the objects have references to one another then if one of the objects is garbage they are all. So having destructors that remove the connection is only useful when someone explicitly calls delete on an object still connected.
Sep 14 2005
parent Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
Ben Hinkle wrote:

Yes, but only to objects (Signals and Slots) that know about each other 
and about their managers (the ones calling deleteSignals and/or 
deleteSlots). In their destructor they deregister themselves with these 
referencing objects. So at the time of destruction, only references exist 
to objects that have not been destructed yet. Therefore, the order of 
destruction does not matter.

Bastiaan.

I should add that if all the objects have references to one another then if one of the objects is garbage they are all. So having destructors that remove the connection is only useful when someone explicitly calls delete on an object still connected.

Yes. So in this case calling delete Object or Object.discard() is somewhat equivalent (where discard() is a method that disconnects all signals and slots of Object). The former is immediate and familiar to C++ programmers, the latter is delayed and a bit special. Bastiaan.
Sep 15 2005
prev sibling parent reply "Uwe Salomon" <post uwesalomon.de> writes:
Indigo also contains a signals&slots implementation. It is partly  
malloc-based to avoid GC problems, and very simple to use (without signal  
managers and other complexity classes). You can have a look at it at:

http://www.uwesalomon.de/code/indigo/files/core/cmdtarget-d.html#Signals_and_slots

Ciao
uwe
Sep 15 2005
parent Bastiaan Veelo <Bastiaan.N.Veelo ntnu.no> writes:
Uwe Salomon wrote:
 Indigo also contains a signals&slots implementation. It is partly  
 malloc-based to avoid GC problems, and very simple to use (without 
 signal  managers and other complexity classes). You can have a look at 
 it at:
 
 http://www.uwesalomon.de/code/indigo/files/core/cmdtarget-d.ht
l#Signals_and_slots 
 
 
 Ciao
 uwe

Nice work. I like the ability to connect partly compatible signals and slots. From the documentation:
 Connections between objects will not detain the garbage collector from
 recycling them if they are not referenced otherwise.

Cool! I will have a closer look. Bastiaan.
Sep 16 2005