TBase=class

public

procedure aaaa();

procedure doaaaa();virtual;

end;

procedure TBase.aaaa()

begin

    doaaaa();

end;

procedure TBase.doaaaa();

begin

     a.function;

end;

————————————————–

TChild=class(TBase)

public

procedure doaaaa();override;

end;

procedure TChile.doaaaa();

begin

b.function;

end;

————————

调用时，TClild 调用aaaa()，将执行b.function;