Virtual constructors

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What is translated > Types > Records, Classes, Interfaces > Class > Constructors > Virtual constructors

In Delphi constructors can be used like virtual functions in C#. This can be demonstrated at the example, which is also used in the section about class method. A class method might be called for a base class and another class derived from it:


pBase := TBase.Create;

pDerived1 := TDerived1.Create;


pDerived1->ClassMethod( pDerived1, 1 );


Inside of the class method a new object of the class is created:


class function TBase.ClassMethod(xi: Integer): Integer;


  with Create do   <-- new object from virtual constructor


    Init;          <-- virtual method




  result := xi;



The Init method might be virtual. In this case the Init method of TDerived1 will be called. That means, an instance of TDerived1 has been created, because ClassMethod was called for a TDerived1 object. If ClassMethod were called for a TBase object, a TBase object would have been created and TBase.Init would have been called.









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