• Joseph Wakeling (28/28) Apr 24 2010 Hello all,
• Robert Clipsham (20/48) Apr 24 2010 This should do what you want:
• Joseph Wakeling (6/7) Apr 25 2010 Thanks! :-)
• Mihail Strashun (1/8) Apr 25 2010
• Robert Clipsham (33/40) Apr 25 2010 Yes it is, providing the base doesn't implement any methods, eg:
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (5/12) Apr 25 2010 Just to be complete: interfaces can have static or final functions in D2...

Joseph Wakeling <joseph.wakeling webdrake.net> writes:

Hello all,

Occasionally in C++ I find it useful to build an array which contains
classes of multiple different types all using the same interface -- by
constructing an array of pointers to some common base class, e.g.

class BaseClass {
    // blah, blah ...
};

class A : BaseClass {
    // ... blah ...
};

class C : BaseClass {
    // ... blah ...
};

int main()
{
    vector<BaseClass *> vec;
    vec.push_back(new A());
    vec.push_back(new C());
    // etc. etc.
}

(This code might be wrong; I'm just typing it to give the idea.  And in
practice, I usually do not use 'new' statements but pass pointers to
already-existing objects...:-)

Anyway, the point is that at the end of the day I have an array of
different objects with a common interface.  What's the appropriate way
to achieve the same effect in D?

Thanks & best wishes,

    -- Joe

Robert Clipsham <robert octarineparrot.com> writes:

On 24/04/10 20:06, Joseph Wakeling wrote:
 Hello all,

 Occasionally in C++ I find it useful to build an array which contains
 classes of multiple different types all using the same interface -- by
 constructing an array of pointers to some common base class, e.g.

 class BaseClass {
      // blah, blah ...
 };

 class A : BaseClass {
      // ... blah ...
 };

 class C : BaseClass {
      // ... blah ...
 };

 int main()
 {
      vector<BaseClass *>  vec;
      vec.push_back(new A());
      vec.push_back(new C());
      // etc. etc.
 }

 (This code might be wrong; I'm just typing it to give the idea.  And in
 practice, I usually do not use 'new' statements but pass pointers to
 already-existing objects...:-)

 Anyway, the point is that at the end of the day I have an array of
 different objects with a common interface.  What's the appropriate way
 to achieve the same effect in D?

 Thanks&  best wishes,

      -- Joe

This should do what you want:
----
class BaseClass {
     // blah, blah ...
}

class A : BaseClass {
     // ... blah ...
}

class C : BaseClass {
     // ... blah ...
}

int main()
{
     BaseClass[] vec;
     vec ~= new A;
     vec ~= new C;
     // etc. etc.
}
----

Joseph Wakeling <joseph.wakeling webdrake.net> writes:

Robert Clipsham wrote:
 This should do what you want:

Thanks! :-)

Is it possible to do this with an interface instead of a base class?
I'm not familiar with how the former work ...

Best wishes,

    -- Joe

Mihail Strashun <m.strashun gmail.com> writes:

On 04/25/2010 04:47 PM, Joseph Wakeling wrote:
 Robert Clipsham wrote:
 This should do what you want:

 Thanks! :-)

 Is it possible to do this with an interface instead of a base class?
 I'm not familiar with how the former work ...

 Best wishes,

      -- Joe

Robert Clipsham <robert octarineparrot.com> writes:

On 25/04/10 14:47, Joseph Wakeling wrote:
 Robert Clipsham wrote:
 This should do what you want:

 Thanks! :-)

 Is it possible to do this with an interface instead of a base class?
 I'm not familiar with how the former work ...

 Best wishes,

      -- Joe

Yes it is, providing the base doesn't implement any methods, eg:

----
interface I
{
   int foobar();
   // The following line will cause an error when uncommented, as
   // you cannot implement methods in an interface
   // void baz() {}
}

class C : I
{
   int foobar() { return 1; }
}

class D : I
{
   int foobar() { return 2; }
}

import std.stdio;

void main()
{
   I[] arr;
   arr ~= new C;
   arr ~= new D;
   foreach( el; arr )
     writefln( "%d", el.foobar() );
}
----
Prints:
1
2

You could also use an abstract class instead of an interface if you want 
to implement some of the methods.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

Robert Clipsham wrote:

 interface I
 {
   int foobar();
   // The following line will cause an error when uncommented, as
   // you cannot implement methods in an interface
   // void baz() {}
 }

Just to be complete: interfaces can have static or final functions in D2:

     static void baz() {}
     final void baz_2() {}

Ali