理解 Delphi 的类(十一) - 深入类中的方法[7] - 关于 inherited

// inherited 就是调用父类方法的一个特殊命令; 举例:



unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure Button1Click(Sender: TObject);

  end;



  {建立父类, 类中包括一个函数 Fun 和一个等待覆盖的虚方法 Proc}

  TBass = class

    procedure Proc; virtual;

    function Fun(x,y: Integer): string;

  end;



  {建立四个子类, 分别覆盖父类的虚方法}

  TChild1 = class(TBass)

    procedure Proc; override;

  end;



  TChild2 = class(TBass)

    procedure Proc; override;

  end;



  TChild3 = class(TBass)

    procedure Proc; override;

  end;



  TChild4 = class(TBass)

    procedure Proc; override;

  end;





var

  Form1: TForm1;



implementation



{$R *.dfm}



{ TBass }

function TBass.Fun(x, y: Integer): string;

begin

  Result := IntToStr(x + y); {父类函数是返回两个数的和}

end;



procedure TBass.Proc;

begin

  ShowMessage('TBass');      {父类的虚方法会弹出信息: TBass}

end;



{ TChild1 }

procedure TChild1.Proc;

begin

  inherited Proc;            {调用父类的 Proc 方法}

end;



{ TChild2 }

procedure TChild2.Proc;

begin

  inherited;                 {调用父类的同名方法可以省略方法名}

  ShowMessage('TChild2');    {然后弹出自己的信息框}

end;



{ TChild3 }

procedure TChild3.Proc;

begin

  ShowMessage('TChild3');    {先弹出自己的信息框}

  inherited;                 {再调用父类的同名方法}

end;



{ TChild4 }

procedure TChild4.Proc;

begin

  ShowMessage(inherited Fun(11,22)); {调用父类的那个求和的函数}

end;





{测试}

procedure TForm1.Button1Click(Sender: TObject);

var

  c1: TChild1;

  c2: TChild2;

  c3: TChild3;

  c4: TChild4;

begin

  c1 := TChild1.Create;

  c2 := TChild2.Create;

  c3 := TChild3.Create;

  c4 := TChild4.Create;



  c1.Proc; {显  示: TBass}

  c2.Proc; {先显示: TBass;   再显示: TChild2}

  c3.Proc; {先显示: TChild3; 再显示: TBass}

  c4.Proc; {显  示: 33; 11+22=33吗}



  c1.Free;

  c2.Free;

  c3.Free;

  c4.Free;

end;



end.