Static Methods

Methods are by default static. When a static method is called, the declared (compile-time) type of the class or object variable used in the method call determines which implementation to activate. In the following example, the Draw methods are static.

type

TFigure = class procedure Draw; end;

TRectangle = class(TFigure)

procedure Draw; end;

Given these declarations, the following code illustrates the effect of calling a static method. In the second call to Figure.Draw, the Figure variable references an object of class TRectangle, but the call invokes the implementation of Draw in TFigure, because the declared type of the Figure variable is

TFigure.

Figure: TFigure; Rectangle: TRectangle;

begin

Figure := TFigure.Create;

  1. Draw; // calls TFigure.Draw
  2. Destroy;

Figure := TRectangle.Create;

Figure.Draw;

// calls TFigure.Draw

TRectangle(Figure).Draw; // calls TRectangle.Draw Figure.Destroy;

Rectangle := TRectangle.Create;

  1. Draw; // calls TRectangle.Draw
  2. Destroy;

end;

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