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#### Virtual methods

Classes have virtual methods, just as objects do. There is however a difference between the two. For objects, it is sufficient to redeclare the same method in a descendent object with the keyword virtual to override it. For classes, the situation is different: virtual methods must be overridden with the override keyword. Failing to do so, will start a new batch of virtual methods, hiding the previous one. The Inherited keyword will not jump to the inherited method, if virtual was used.

The following code is wrong:

     Type ObjParent = Class
             Procedure MyProc; virtual;
          end;
          ObjChild  = Class(ObjPArent)
            Procedure MyProc; virtual;
          end;

The compiler will produce a warning:

     Warning: An inherited method is hidden by OBJCHILD.MYPROC

The compiler will compile it, but using Inherited can produce strange effects.

The correct declaration is as follows:

     Type ObjParent = Class
             Procedure MyProc; virtual;
          end;
          ObjChild  = Class(ObjPArent)
            Procedure MyProc; override;
          end;

This will compile and run without warnings or errors.

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