在今后的 Delphi 中, 以接口、结构为主的设计应该会越来越多, 因为这样太方便了.

System.RegularExpressions 就是以结构为主体设计的非常好的示范; 但更多东西使用接口会更合适.

有见过他人早就使用接口写程序, 从手头的这个程序开始我才开始使用.

现在基本总结出四种框架模式: 1、直接实现; 2、间接实现(或叫继承实现); 3、覆盖实现; 4、委托实现.

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一、直接实现:

下例中虽有 TMy1、TMy2, 但在具体应用中使用的应是 IMy1、IMy2, 这就是我所谓的以接口为主导.

TMy1、TMy2 直接实现了所属接口的所有方法, 这是我所谓的直接实现.

这样可能会有代码重复, 但如果程序很小, 还是挺实用的.

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unit Unit1;interfaceuses  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,  Vcl.Controls, Vcl.Forms, Vcl.Dialogs;type  TForm1 = class(TForm)    procedure FormCreate(Sender: TObject);  end;  IA = Interface    procedure Method_A;  end;  IB = Interface(IA)    procedure Method_B;  end;  IMy1 = Interface(IB)    procedure Method_My1;  end;  IMy2 = Interface(IB)    procedure Method_My2;  end;  TMy1 = class(TInterfacedObject, IMy1)    procedure Method_A;    procedure Method_B;    procedure Method_My1;  end;  TMy2 = class(TInterfacedObject, IMy2)    procedure Method_A;    procedure Method_B;    procedure Method_My2;  end;var  Form1: TForm1;implementation{$R *.dfm}{ TMy1 }procedure TMy1.Method_A;begin  ShowMessage('A');end;procedure TMy1.Method_B;begin  ShowMessage('B');end;procedure TMy1.Method_My1;begin  ShowMessage('My1');end;{ TMy2 }procedure TMy2.Method_A;begin  ShowMessage('A');end;procedure TMy2.Method_B;begin  ShowMessage('B');end;procedure TMy2.Method_My2;begin  ShowMessage('My2');end;{测试}procedure TForm1.FormCreate(Sender: TObject);var  v1: IMy1;  v2: IMy2;begin  v1 := TMy1.Create;  v1.Method_A;  v1.Method_B;  v1.Method_My1;  v2 := TMy2.Create;  v2.Method_A;  v2.Method_B;  v2.Method_My2;end;end.

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二、间接实现:

下面例子通过一个间接的 TB 类, 避免了 TMy1、TMy2 中可能会重复的代码.

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unit Unit1;interfaceuses  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,  Vcl.Controls, Vcl.Forms, Vcl.Dialogs;type  TForm1 = class(TForm)    procedure FormCreate(Sender: TObject);  end;  IA = Interface    procedure Method_A;  end;  IB = Interface(IA)    procedure Method_B;  end;  TB = class(TInterfacedObject, IB)    procedure Method_A;    procedure Method_B;  end;  IMy1 = Interface(IB)    procedure Method_My1;  end;  IMy2 = Interface(IB)    procedure Method_My2;  end;  TMy1 = class(TB, IMy1)    procedure Method_My1;  end;  TMy2 = class(TB, IMy2)    procedure Method_My2;  end;var  Form1: TForm1;implementation{$R *.dfm}{ TB }procedure TB.Method_A;begin  ShowMessage('A');end;procedure TB.Method_B;begin  ShowMessage('B');end;{ TMy1 }procedure TMy1.Method_My1;begin  ShowMessage('My1');end;{ TMy2 }procedure TMy2.Method_My2;begin  ShowMessage('My2');end;{测试}procedure TForm1.FormCreate(Sender: TObject);var  v1: IMy1;  v2: IMy2;begin  v1 := TMy1.Create;  v1.Method_A;  v1.Method_B;  v1.Method_My1;  v2 := TMy2.Create;  v2.Method_A;  v2.Method_B;  v2.Method_My2;end;end.

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三、覆盖实现:

从 TB 继承的过程中当然也可以通过覆盖虚函数而实现多态, 下面的 TMy2 就这么做了.

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unit Unit1;interfaceuses  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,  Vcl.Controls, Vcl.Forms, Vcl.Dialogs;type  TForm1 = class(TForm)    procedure FormCreate(Sender: TObject);  end;  IA = Interface    procedure Method_A;  end;  IB = Interface(IA)    procedure Method_B;  end;  TB = class(TInterfacedObject, IB)    procedure Method_A; virtual;    procedure Method_B; virtual;  end;  IMy1 = Interface(IB)    procedure Method_My1;  end;  IMy2 = Interface(IB)    procedure Method_My2;  end;  TMy1 = class(TB, IMy1)    procedure Method_My1;  end;  TMy2 = class(TB, IMy2)    procedure Method_A; override;    procedure Method_B; override;    procedure Method_My2;  end;var  Form1: TForm1;implementation{$R *.dfm}{ TB }procedure TB.Method_A;begin  ShowMessage('A');end;procedure TB.Method_B;begin  ShowMessage('B');end;{ TMy1 }procedure TMy1.Method_My1;begin  ShowMessage('My1');end;{ TMy2 }procedure TMy2.Method_A;begin  ShowMessage('A_My2');end;procedure TMy2.Method_B;begin  ShowMessage('B_My2');end;procedure TMy2.Method_My2;begin  ShowMessage('My2');end;{测试}procedure TForm1.FormCreate(Sender: TObject);var  v1: IMy1;  v2: IMy2;begin  v1 := TMy1.Create;  v1.Method_A;  v1.Method_B;  v1.Method_My1;  v2 := TMy2.Create;  v2.Method_A;  v2.Method_B;  v2.Method_My2;end;end.

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四、委托实现:

接口中的方法是肯定要实现的, 但也可以通过 implements 关键字借用(或叫委托)其它的实现;

但, 官方文档说这只适用于 Win32. 就是说这种方法在 Win64 和其它系统都不行, 还学它干嘛?

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