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digitalmars.D - Automatic Interface Implementation

reply "JS" <js.mdnq gmail.com> writes:
I ripped and hacked up some code from typecons that allows one to 
implement an interface automatically by redirecting it to a 
variable implementing the interface.

http://dpaste.dzfl.pl/209e260b

To see the effectiveness of the code, notice that very little, if 
any, boilerplate code needs to be used to implement such a 
pattern:


interface A
{
	void foo();
	void foo2();
	int bar(int x);
	void bar(string c);
}

// Dummy class for A
class AA : A { void foo() { writeln("AA.foo");  } void foo2() { 
writeln("AA.foo2"); } int bar(int x) { writeln("AA.bar(int)"); 
return 0; }  void bar(string c) { writeln("AA.bar(string)"); } }

class B : A
{
	A a;

	void foo2() { writeln("B.foo2"); }
	mixin implementComposite!a;
}


I'm not sure how this code holds up though, it's possible 
templated classes and other more complex implementations may 
cause some problems....

It will probably do fine for what I need it to do but maybe 
someone else will find it useful or can make it better...
Jul 05 2013
parent reply "Vladimir Panteleev" <vladimir thecybershadow.net> writes:
On Friday, 5 July 2013 at 17:53:11 UTC, JS wrote:

 I ripped and hacked up some code from typecons that allows one 
 to implement an interface automatically by redirecting it to a 
 variable implementing the interface.


How about splitting up the implementation of AutoImplement into a 
template mixin, which would then be usable on its own?

Some previous discussion on the topic:

http://forum.dlang.org/post/20100909021137.40d2dce2.rsinfu gmail.com

The new "wrap" from std.typecons looks like it might help, 
however:
1) The type it creates is completely inaccessible (the return 
type is the interface);
2) It doesn't seem to play well with "alias this". Instead of 
wrapping methods in the struct containing "alias this", it uses 
the methods (with the same name/signature) from the object "alias 
this" points to.
Jul 05 2013
next sibling parent reply "JS" <js.mdnq gmail.com> writes:
On Friday, 5 July 2013 at 22:33:01 UTC, Vladimir Panteleev wrote:

 On Friday, 5 July 2013 at 17:53:11 UTC, JS wrote:

 I ripped and hacked up some code from typecons that allows one 
 to implement an interface automatically by redirecting it to a 
 variable implementing the interface.


 How about splitting up the implementation of AutoImplement into 
 a template mixin, which would then be usable on its own?

 Some previous discussion on the topic:

 http://forum.dlang.org/post/20100909021137.40d2dce2.rsinfu gmail.com

 The new "wrap" from std.typecons looks like it might help, 
 however:
 1) The type it creates is completely inaccessible (the return 
 type is the interface);
 2) It doesn't seem to play well with "alias this". Instead of 
 wrapping methods in the struct containing "alias this", it uses 
 the methods (with the same name/signature) from the object 
 "alias this" points to.


I took the code from the latest std.typecons wrap and modified 
it(well, after initially doing my own interface). I just needed a 
quick implementation.

std.typecon has a lot of goodies in it but it seems to 
re-implement much of the same functionality in many of the 
templates.

wrap did not compile do I took out the stuff that didn't work and 
hacked it up to get what I needed out of it.
Jul 05 2013
parent reply "Vladimir Panteleev" <vladimir thecybershadow.net> writes:
On Friday, 5 July 2013 at 22:43:06 UTC, JS wrote:

 std.typecon has a lot of goodies in it but it seems to 
 re-implement much of the same functionality in many of the 
 templates.


I agree, it would be nice if it would be broken up into smaller, 
reusable pieces that would also be usable from user code for 
tasks such as yours.


 wrap did not compile do I took out the stuff that didn't work 
 and hacked it up to get what I needed out of it.


Here is my attempt at using it:

http://dump.thecybershadow.net/9562c8f705cb578be1e1513b6f931fb8/test.d

However, calling b.foo2 prints AA.foo2 instead of B.foo2 due to 
the bug I mentioned.
Jul 05 2013
parent "JS" <js.mdnq gmail.com> writes:
On Friday, 5 July 2013 at 23:22:23 UTC, Vladimir Panteleev wrote:

 On Friday, 5 July 2013 at 22:43:06 UTC, JS wrote:

 std.typecon has a lot of goodies in it but it seems to 
 re-implement much of the same functionality in many of the 
 templates.


 I agree, it would be nice if it would be broken up into 
 smaller, reusable pieces that would also be usable from user 
 code for tasks such as yours.


 wrap did not compile do I took out the stuff that didn't work 
 and hacked it up to get what I needed out of it.


 Here is my attempt at using it:

 http://dump.thecybershadow.net/9562c8f705cb578be1e1513b6f931fb8/test.d

 However, calling b.foo2 prints AA.foo2 instead of B.foo2 due to 
 the bug I mentioned.


Since I do not have wrap to try it out(Kenji suggested using it 
in another post which is when I started looking at the typecons 
source) and as far as I can tell it actually wraps a type rather 
than just implements functions for an interface, it is not 
exactly what I needed, but code wise, pretty close. I didn't need 
to create a new wrapper class but just mixin the implementations 
of an interface(although, in theory, one could also use it for 
abstract methods).
Jul 05 2013
prev sibling parent reply "John Colvin" <john.loughran.colvin gmail.com> writes:
On Friday, 5 July 2013 at 22:33:01 UTC, Vladimir Panteleev wrote:

 The new "wrap" from std.typecons


Yikes... I'm a native english speaker and pretty confident with D 
but I can't get my head around what wrap does. It looks 
suspiciously like the docs were written by a Russian (missing 
articles :) ).

Any chance you could provide an explanation for me?
Jul 05 2013
next sibling parent "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Sat, Jul 06, 2013 at 12:54:37AM +0200, John Colvin wrote:

 On Friday, 5 July 2013 at 22:33:01 UTC, Vladimir Panteleev wrote:

The new "wrap" from std.typecons


 
 Yikes... I'm a native english speaker and pretty confident with D
 but I can't get my head around what wrap does. It looks suspiciously
 like the docs were written by a Russian (missing articles :) ).


The docs could use actual code examples to show what it does, instead of
relying on mere words. :-/ I'd say file a bug in the bugtracker if there
isn't one already.



 Any chance you could provide an explanation for me?


I just read the docs, and I'm just as confused as you are. :-(


T

-- 
It is the quality rather than the quantity that matters. -- Lucius Annaeus
Seneca
Jul 05 2013
prev sibling next sibling parent "Vladimir Panteleev" <vladimir thecybershadow.net> writes:
On Friday, 5 July 2013 at 22:54:38 UTC, John Colvin wrote:

 On Friday, 5 July 2013 at 22:33:01 UTC, Vladimir Panteleev 
 wrote:

 The new "wrap" from std.typecons


 Yikes... I'm a native english speaker and pretty confident with 
 D but I can't get my head around what wrap does. It looks 
 suspiciously like the docs were written by a Russian (missing 
 articles :) ).

 Any chance you could provide an explanation for me?


I agree, the docs are rather terse. I only know about it because 
quite a while ago, Kenji posted[1] some code including adaptTo. 3 
years later, it made it into Phobos.

What it does, is:

Let's say you have a struct S, and an interface I, which both 
have (some of) the same methods. You'd like to refer to an 
instance of S through the I interface.

Now, a D interface is just a vtable, but structs can't have 
virtual methods or inheritance. To do that (by hand), you'd 
declare a class which inherits from I, contains a copy of S, and 
for each method in I, it implements it by forwarding the call to 
its copy of S.

The wrap function template does this for you - it generates the 
class, instantiates it, initializes its copy of S, and returns an 
I that points to the new class instance.

Feel free to send a pull request to improve the documentation. 
(You can use GitHub's "Edit" button to do it without leaving the 
browser.)

   [1]: 
http://forum.dlang.org/post/mailman.286.1285099532.858.digitalmars-d puremagic.com
Jul 05 2013
prev sibling parent "Michael" <pr m1xa.com> writes:
It's looks like he modify a source code from std.typecons 
(something like class AutoImplement?) and a new thing called 
"wrap" was created.

Like two fingers on the asphalt)))))
Jul 05 2013