Delphi for .NET Developer’s Guide

Constructors

One simple rule about constructors in Delphi for .NET is different from Delphi Win32. You cannot access class members from inherited classes prior to calling the inherited constructor. This will result in a compile-time error. You can access members of the class itself. So, for the given classes, the comments annotate the valid and invalid statements within the constructor.

TMyBase = class(TObject)
  FBaseField: integer;
end;

TMyObject = class(TMyBase)
  FMyObjectField: integer;
  constructor Create;
end;

The implementation of the preceding constructor above would be

constructor TMyObject.Create;
begin
  FBaseField := 3; // error
  FMyObjectField := 3; // valid
  inherited;
  FBaseField := 3; // valid
  FMyObjectField := 3; // valid
end;