[SOLVED] Abstract Generic Class uses wrong procedure

[Jan_]

Hi,
i got the Runtime Error: Call to abstract method
Main file

Code: Pascal  [Select][+][-]

1. program fluent_interfaces_1;
2.  
3. {$interfaces CORBA}
4.  
5. uses MapBuilder0_fluent , MapBuilder0Impl_fluent , MapBuilderAction_fluent ;
6.  
7. type
8.  
9.    TMapBuilder0Impl =specialize MapBuilder0Impl<String,Integer>;
10.    TMapBuilderAction=specialize MapBuilderAction<String,Integer>;
11.  
12.   MapB = class(TMapBuilder0Impl)
13.     constructor Create;
14.   end;
15.  
16.    MapBuilderImpl = class(TMapBuilderAction )
17.      public
18.          procedure  put( key:String;  value:Integer); override;
19.    end;
20.  
21.  
22. //MapB
23. Constructor MapB.Create;
24. var
25.   myaction:TMapBuilderAction;
26. begin
27.   myaction:=TMapBuilderAction.Create;
28.   Inherited create(myaction);
29. end;
30.  
31. //MapBuilderImpl
32. procedure  MapBuilderImpl.put( key:String;  value:Integer);
33. begin
34.     WriteLn('PUT');
35. end;
36.  
37. begin
38.   MapB.Create().put('Hallo',0).put('Hallo',1);
39.   readln();
40. end.
41.  
42.  
43.  
44.  

MapBuilder0_fluent

Code: Pascal  [Select][+][-]

1. unit MapBuilder0_fluent;
2.  
3. //generateIState
4. {$interfaces CORBA}
5.  
6. interface
7.  
8.  
9. type
10.     generic MapBuilder0 <K, V>= interface
11.   function put( key:K;  value:V):specialize MapBuilder0<K, V>;
12. End;
13. implementation
14. End.
15.  

MapBuilder0Impl_fluent

Code: Pascal  [Select][+][-]

1. unit MapBuilder0Impl_fluent;
2.  
3. //generateState
4. interface
5. uses MapBuilderAction_fluent , MapBuilder0_fluent;
6.  
7. Type  
8.   generic MapBuilder0Impl <K, V>= Class(TInterfacedObject,specialize MapBuilder0<K, V>)
9.   private
10.     action:specialize MapBuilderAction<K, V>;
11.  
12.   public
13.     Constructor Create(myaction:specialize MapBuilderAction<K, V>);
14.   function build():Integer;
15.   procedure print();
16.   function put( key:K;  value:V):specialize MapBuilder0<K, V>;
17. End;
18.  
19. implementation
20.  
21. Constructor MapBuilder0Impl.Create(myaction:specialize MapBuilderAction<K, V>);
22. Begin
23.   Self.action := myaction;
24. End;
25.  
26. function MapBuilder0Impl.put( key:K;  value:V):specialize MapBuilder0<K, V>;
27. Begin
28.       Self.action.state0_put(key, value);
29.       exit( MapBuilder0Impl.Create(Self.action));
30. End;
31. End.

MapBuilderAction_fluent

Code: Pascal  [Select][+][-]

1. unit MapBuilderAction_fluent;
2.  
3. //generateIAction
4. interface
5.  
6. type
7.   generic MapBuilderAction <K, V>= Class Abstract
8.   procedure  state0_put( key:K;  value:V);
9.   procedure  put( key:K;  value:V); virtual; abstract;
10. End;
11.  
12. implementation
13.  
14. procedure  MapBuilderAction.state0_put( key:K;  value:V);
15. Begin
16.     put(key, value);
17. End;
18.  
19. End.

in the procedure procedure  MapBuilderAction.state0_put( key:K;  value:V); i got the Error.
i do not see, why it not calls MapBuilderImpl.put( key:String;  value:Integer)
and how can i solve the Problem?

[Zvoni]

??
https://www.freepascal.org/docs-html/ref/refse36.html

An abstract class is a class that cannot be instantiated directly. Instead, a descendent class must always be instantiated

[Thaddy]

 procedure  state0_put( key:K;  value:V);virtual; // this one is not abstract, so for inheritance to work it should be virtual in first implementation?
 

[PascalDragon]

in the procedure procedure  MapBuilderAction.state0_put( key:K;  value:V); i got the Error.
i do not see, why it not calls MapBuilderImpl.put( key:String;  value:Integer)
and how can i solve the Problem?

In MapB.Create you do

Code: Pascal  [Select][+][-]

1. myaction:=TMapBuilderAction.Create;

but instead it should be

Code: Pascal  [Select][+][-]

1. myaction:=MapBuilderImpl.Create;

procedure  state0_put( key:K;  value:V);virtual; // this one is not abstract, so for inheritance to work it should be virtual in first implementation?

state0_put is fine as it is. It does not need to be virtual (at least not for the presented example).

[Jan_]

Realy big Thank Pascal Dragon.