Declaring the Class Fields

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Go Up to Publishing the Pen and Brush

Each class a component owns must have a class field declared for it in the component. The class field ensures that the component always has a pointer to the owned object so that it can destroy the class before destroying itself. In general, a component initializes owned objects in its constructor and destroys them in its destructor.

Fields for owned objects are nearly always declared as private. If applications (or other components) need access to the owned objects, you can declare published or public properties for this purpose.

Add fields for a pen and brush to the shape control:

   TSampleShape = class(TGraphicControl)
   private            { fields are nearly always private }
     FPen: TPen;      { a field for the pen object }
     FBrush: TBrush;  { a field for the brush object }
 class PACKAGE TSampleShape : public TGraphicControl
 private:               // data members are always private
     TPen *FPen;        // a data member for the pen object
     TBrush *FBrush;    // a data member for the brush object

See Also