《GOF设计模式》—桥接（BRIDGE）—Delphi源码示例：仅有一个Implementor


示例：仅有一个Implementor
说明：
在仅有一个实现的时候，没有必要创建一个抽象的Implementor类。这是Bridge模式的退化情况；在Abstraction与Implementor之间有一种一对一的关系。尽管如此，当你希望改变一个类的实现不会影响已有的客户程序时，模式的分离机制还是非常有用的—也就是说，不必重新编译它们，仅需重新连接即可（例如，Abstraction在主程序实现，Implementor在DLL中实现）。

代码：

unit uBridge1;

interface

uses

Dialogs;

type

TImplementor = class;

{抽象类}

TAbstraction = class

private

FImp: TImplementor;

public

constructor Create(AImplementor: TImplementor);

//---

procedure Operation; virtual;

end;

TRefinedAbstraction = class(TAbstraction)

public

procedure Operation; override;
end;

{实现类}

TImplementor = class

procedure OperationImp;

end;

implementation

constructor TAbstraction.Create(AImplementor: TImplementor);
begin

FImp := AImplementor;
end;

procedure TAbstraction.Operation;
begin

FImp.OperationImp;
end;

procedure TImplementor.OperationImp;
begin

ShowMessage('Implementor');
end;

procedure TRefinedAbstraction.Operation;
begin

inherited;

//---

ShowMessage('Refined');
end;

end.

procedure TForm1.Button1Click(Sender: TObject);
var

AImplementor: TImplementor;

AAbstraction: TAbstraction;
begin

AImplementor := TImplementor.Create;

AAbstraction := TRefinedAbstraction.Create(AImplementor);

try

AAbstraction.Operation;

finally

AAbstraction.Free;

AImplementor.Free;

end;
end;