Parent class inside another class

Question

Okay, so I have this class, let's say CMain, that contains a CFruit class. What I would like to do is run functions based on CFruit's type (if it's CPear or CApple, etc). So I'd like to do something like this:

type CMain = class
   myFruit : CFruit;
   function GetFruit() : CFruit;
   procedure SetFruit( Fruit : CFruit ); 
end;

procedure CMain.SetFruit( Fruit : CFruit );
begin
  if Fruit.IsPear then .. else etc;
end;

...obviously the compiler stops me from doing this because CFruit is just CPear and CApple's parent. Is there any viable way I can do this? (making sepparate CMain's is out of the question). Thanks.

Answer 1

Here is an example for the use of virtual methods:

type 
TFruit = class
public
  procedure doSomethingFruitSpecific; virtual; abstract;
end;

TPear = class(TFruit)
public
  procedure doSomethingFruitSpecific; override;
end;

TApple = class(TFruit)
public
  procedure doSomethingFruitSpecific; override;
end;

TMain = class
   procedure SetFruit( Fruit : TFruit ); 
end;

implementation

procedure TMain.SetFruit( Fruit : TFruit );
begin
  Fruit.doSomethingFruitSpecific;
end;

procedure TApple.doSomethingFruitSpecific;
begin
  Writeln('bake an apple pie');
end;

procedure TPear.doSomethingFruitSpecific;
begin
  Writeln('pick some pears');
end;