Constructor inheritance issue

Question

I have two classes, a base class and a derived class. My base class has a constructor of this form:

constructor TBaseClass.CreateFromXML(ANode: IXMLNode);
begin

  Create;

  //Set members from XML

end;

My derived class has a constructor of this form:

constructor TDerivedClass.Create;
begin

   FDatabaseID = -1;

end;

My problem is that when I create an object of my derived class using the constructor from the base class [ TDerivedClass.CreateFromXML(Node); ] the Create called at the beginning of the CreateFromXML constructor is not the one from my derived class, but rather the one inherited by my base class from TObject.

Is it possible to get the base class constructor to call my derived class constructor even though it's further "down" the inheritance chain?

If you need derived code to execute at a certain time during creation you should probably just use an event. That would be more elegant than trying to give the base class knowledge of the derived class. — Steven Hook
– Steven Hook, Commented Aug 4, 2010 at 12:11

Uli Gerhardt · Accepted Answer · 2010-08-04 12:08:26Z

9

Try declaring a constructor Create; virtual; in TBaseClass. Don't forget to mark the "derived" constructor as override.

answered Aug 4, 2010 at 12:08

Uli Gerhardt

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1 Comment

Larry Lustig Over a year ago

Just so, thank you. It's been a long time since I encountered this situation; thanks for the reminder!

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