Delphi子类调用祖父类的虚函数

因为看Delphi书的时候，就产生了疑惑。老讲调用父类虚函数，但是万一需要调用祖父虚函数怎么办？
后来又经常在C++里看到，就更疑惑了

type

  TA = class

    procedure ShowMsg; virtual;

  end;

  TAClass = class of TA;

  TB = class(TA)

    procedure ShowMsg; override;

  end;

  TShowMsg = procedure of object;

  TC = class(TB)

  private

    FGrandFatherShowMsg: TShowMsg;

    procedure ShowMsg; override;

  public

    constructor Create;

  end;

procedure TForm2.Button1Click(Sender: TObject);

var

  C: TC;

begin

  C := TC.Create;

  C.ShowMsg;

  C.Free;

end;

{ TC }

constructor TC.Create;

var

  AMethod:TShowMsg;

  ACode: TMethod absolute AMethod;

  A: TA;

begin

  inherited Create;

  A := TA.Create;

  FGrandFatherShowMsg := A.ShowMsg;

  AMethod:= FGrandFatherShowMsg;

  ACode.Data := Self;

  A.Free;

end;

procedure TC.ShowMsg;

begin

  FGrandFatherShowMsg;

  ShowMessage('TC');

end;

{ TA }

procedure TA.ShowMsg;

begin

  ShowMessage('TA');

end;

{ TB }

procedure TB.ShowMsg;

begin

  inherited;

  ShowMessage('TB');

end;

利用了 Delphi 能够创建纯虚函数实例的特性
记录下了TA的函数地址
然后替换其Data的值为Self，然后在需要的时候再调用
利用了两点：TMethod和Delphi能够创建纯虚类实例
只是说万一纯虚的话，这个也好使

感谢 [长春]swish

----------------------------------------------------------

另一种办法：

type

  TBase = class

    procedure Foo; virtual;

  end;

  TAnsestor = class(TBase)

    procedure Foo; override;

  end;

  TChild = class(TAnsestor)

    procedure Foo; override;

    procedure BaseFoo;

  end;

procedure TBase.Foo;

begin

  ShowMessage('TBase');

end;

procedure TAnsestor.Foo;

begin

  ShowMessage('TAnsestor');

end;

procedure TChild.Foo;

begin

  ShowMessage('TChild');

end;

type

  TFoo = procedure of object;

procedure TChild.BaseFoo;

var

  Proc: TFoo;

begin

  TMethod(Proc).Code := @TBase.Foo; // Static address

  TMethod(Proc).Data := Self;

  Proc();

end;

procedure TForm4.Button1Click(Sender: TObject);

var

  Obj: TChild;

  Proc: TFoo;

begin

  Obj:= TChild.Create;

  Obj.BaseFoo;

// or else

  TMethod(Proc).Code := @TBase.Foo; // Static address

  TMethod(Proc).Data := Obj;

  Proc();

  Obj.Free;

end;

http://stackoverflow.com/questions/4662744/delphi-how-to-call-inherited-inherited-ancestor-on-a-virtual-method

诀窍是搜索关键字“delphi inherited super parent”

巴特西

Delphi子类调用祖父类的虚函数

最新文章

热门文章