delphi - 如何用 2 个或更多类实现相同的方法？

Question

我想编写一个具有 3 个相同方法的 TCheckBox 和 TRadioButton 后代。

TMyCheckBox = class(TCheckBox)
  procedure DoSomething1;
  procedure DoSomething2;
  procedure WMSize(var Message: TWMSize); message WM_SIZE;
end;

TMyRadioButton = class(TRadioButton)
  procedure DoSomething1;
  procedure DoSomething2;
  procedure WMSize(var Message: TWMSize); message WM_SIZE;
end;

// the following procedures are common for both classes, so in fact
// TMyCheckBox.DoSomething1 do the same as TMyRadioButton.DoSomething1

procedure DoSomething1;
begin
  // here is the same code for TMyCheckBox as well as for TMyRadioButton
  // but I don't want to write the same code many times but implement it
  // for both classes at once in some common way
end;

procedure DoSomething2;
begin
  // here is the same code for TMyCheckBox as well as for TMyRadioButton
  // but I don't want to write the same code many times but implement it
  // for both classes at once in some common way
end;

procedure WMSize(var Message: TWMSize); message WM_SIZE;
begin
  // here is the same code for TMyCheckBox as well as for TMyRadioButton
  // but I don't want to write the same code many times but implement it
  // for both classes at once in some common way
end;

我该怎么做？

Answer 1

使用三个方法签名定义一个接口(interface)，例如IDoSomething。

然后将您的类声明更改为

TMyCheckBox = class(TCheckBox, IDoSomething)

然后实现。

实现是否常见或非常接近。

然后定义一个辅助类TDoSomething，然后委派工作。

例如

Procedure TMyCheckBox.DoSomething1; // implements IDoSomething1
Begin
  TDoSomething.DoSomething1(Self); // given class method will suffice.
End;

delphi中的类方法，相当于其他语言中的静态方法。

Type
    TDoSomethingHelper = Class(TObject)
    Public
      Class Procedure DoSomething1(aComponent : TComponent);
    End;

...
implementation

Class Procedure TDoSomethingHelper.DoSomething1(aComponent : TComponent);
Begin
  aComponent.Tag = 27;
End;