local casting to interface

[Чебурашка]

My idea was of using inteface in order to call from unrelated class by local casting but it doesn't work.

Is there a way to get this working?

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. {$INTERFACES CORBA}
4.  
5. type
6.  
7.   IExample = interface
8.     procedure SomeMethod();
9.   end;
10.  
11.   TExampleImplementation = class(TObject, IExample)
12.     public
13.       procedure SomeMethod();
14.   end;
15.  
16. { TExampleImplementation }
17.  
18. procedure TExampleImplementation.SomeMethod();
19. begin
20.   Writeln('In TExampleImplementation.SomeMethod();');
21. end;
22.  
23. var
24.   o: TObject;
25. begin
26.   o := TExampleImplementation.Create();
27.   TExampleImplementation(o).SomeMethod(); // Works, but is fairly useless
28.   IExample(o).SomeMethod(); // <<-- This is the one needed, but gives error: Class or Object types "TObject" and "IExample" are not related
29.   o.Destroy();
30. end.
31.  

[Zvoni]

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. {$INTERFACES CORBA}
4.  
5. type
6.  
7.   IExample = interface
8.     procedure SomeMethod();
9.   end;
10.  
11.   TExampleImplementation = class(TObject, IExample)
12.     public
13.       procedure SomeMethod();
14.   end;
15.  
16. { TExampleImplementation }
17.  
18. procedure TExampleImplementation.SomeMethod();
19. begin
20.   Writeln('In TExampleImplementation.SomeMethod();');
21. end;
22.  
23. var
24. //THIS ONE
25.   o: IExample;
26. begin
27.   o := TExampleImplementation.Create();
28.   o.SomeMethod(); // <<-- This is the one needed, but gives error: Class or Object types "TObject" and "IExample" are not related
29.   //o.Destroy();
30. end.                            

No idea about Freeing/Destroying

[cdbc]

Hi
Yes! Have a look here:

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. {$INTERFACES CORBA}
4. const { this is instrumental }
5.   SGUIDIExample = '{128CE0DE-B11C-4FEB-89AA-38EC3E79F120}';
6. type
7.  
8.   IExample = interface[SGUIDIExample]
9.     procedure SomeMethod();
10.   end;
11.  
12.   TExampleImplementation = class(TObject, IExample)
13.     public
14.       procedure SomeMethod();
15.   end;
16.  
17. { TExampleImplementation }
18.  
19. procedure TExampleImplementation.SomeMethod();
20. begin
21.   Writeln('In TExampleImplementation.SomeMethod();');
22. end;
23.  
24. var
25.   ie: IExample; { we need a variable of the right type }
26.   o: TObject;
27. begin
28.   o := TExampleImplementation.Create();
29.   TExampleImplementation(o).SomeMethod(); // Works, but is fairly useless
30.   { if "o" supports/implements IExample, we get a hold of it and use it... }
31.   if o.GetInterface(SGUIDIExample,ie) then ie.SomeMethod()
32.   else writeln(o.Classname,' does not support IExample');
33.   o.Destroy();
34. end.
35.  

The nice thing about it all, is, "GetInterface" is implemented in TObject 
Ps.: Checkout the implementation of "TPersistent" 
edit: typo
HTH
Regards Benny

[Чебурашка]

Sorry, my very bad. Is was simply:

Code: Pascal  [Select][+][-]

1.   (o as IExample).SomeMethod();
2.  

[Zvoni]

Hi
Yes! Have a look here:
The nice thing about it all, is, "GetInterface" is implemented in TObject 
Ps.: Checkout the implementation of "TPersistence" 
HTH
Regards Benny

So i was actually pretty close... *g*

[Чебурашка]

{$INTERFACES CORBA}

AFAIK with CORBA way user must handle memory management, so without destroy at end there's a memleak.

[cdbc]

Hi
You are correct in this:

AFAIK with CORBA way user must handle memory management, so without destroy at end there's a memleak.

However, you can play a little with corba-interfaces, e.g.:

Code: Pascal  [Select][+][-]

1. program project1;
2.  
3. {$INTERFACES CORBA}
4. const { this is instrumental }
5.   SGUIDIExample = '{128CE0DE-B11C-4FEB-89AA-38EC3E79F120}';
6. type
7.  
8.   IExample = interface[SGUIDIExample]
9.     function Obj: TObject;
10.     procedure SomeMethod();
11.   end;
12.  
13.   TExampleImplementation = class(TObject, IExample)
14.     private
15.       function Obj: TObject;
16.     public
17.       procedure SomeMethod();
18.   end;
19.  
20. { TExampleImplementation }
21. function TExampleImplementation.Obj: TObject;
22. begin
23.   Result:= Self;
24. end;
25.  
26. procedure TExampleImplementation.SomeMethod();
27. begin
28.   Writeln('In TExampleImplementation.SomeMethod();');
29. end;
30.  
31. var
32.   ie: IExample; { we need a variable of the right type }
33.   o: TObject;
34. begin
35.   o := TExampleImplementation.Create();
36.   TExampleImplementation(o).SomeMethod(); // Works, but is fairly useless
37.   { if "o" supports/implements IExample, we get a hold of it and use it... }
38.   if o.GetInterface(SGUIDIExample,ie) then ie.SomeMethod()
39.   else writeln(o.Classname,' does not support IExample');
40.  
41.   { now you have a choice, use either "o" or "ie" NOT both }
42.   ie.Obj.Free; // <--- option 1 \o/\o/\o/
43.   ie:= nil; { no dangling dead references. DON'T TOUCH "o" after this }
44.   ...or...
45.   o.Destroy(); // <--- option 2
46.   //
47. end.
48.  

With the extra function, you can send the interface through an entire framework and free it when it's done its job, you don't need to hold on to the creating object.
Works to/from libraries also, I use only corba interfaces in my Plugin Framework, that way I have finer control over the memory-management.
Have fun 
Regards Benny