Delphi 设计模式：《HeadFirst设计模式》Delphi7代码---模板方法模式之CoffeineBeverageWithHook[转]

模板方法模式定义了一个算法骨架，允许子类对算法的某个或某些步骤进行重写（override)。

  1
  2{《HeadFirst设计模式》之模板方法模式 }
  3{ 编译工具: Delphi7.0              }
  4{ E-Mail : [email protected]      }
  5
  6unit uCoffeineBeverageWithHook;
  7
  8interface
  9
 10uses
 11  SysUtils;
 12
 13type
 14  TCoffeineBeverageWithHook = class(TObject)
 15  protected
 16    procedure BoilWater;
 17    procedure Brew; virtual; abstract;
 18    procedure PourInCup;
 19    procedure AddCondiments; virtual; abstract;
 20    function CustomerWantsCondiments: Boolean; virtual; { 钩子 }
 21  public
 22    procedure PrepareRecipe; { 模板方法 }
 23  end;
 24
 25  TCoffeeWithHook = class(TCoffeineBeverageWithHook)
 26  private
 27    function GetUserInput: string;
 28  public
 29    procedure Brew; override;
 30    procedure AddCondiments; override;
 31    function CustomerWantsCondiments: Boolean; override;
 32  end;
 33
 34  TTeaWithHook = class(TCoffeineBeverageWithHook)
 35  private
 36    function GetUserInput: string;
 37  public
 38    procedure Brew; override;
 39    procedure AddCondiments; override;
 40    function CustomerWantsCondiments: Boolean; override;
 41  end;
 42
 43implementation
 44
 45{ TCoffeineBeverageWithHook }
 46
 47procedure TCoffeineBeverageWithHook.BoilWater;
 48begin
 49  Writeln(‘Boiling Water‘);
 50end;
 51
 52function TCoffeineBeverageWithHook.CustomerWantsCondiments: Boolean;
 53begin
 54  Result := True;
 55end;
 56
 57procedure TCoffeineBeverageWithHook.PourInCup;
 58begin
 59  Writeln(‘Poiling into cup‘);
 60end;
 61
 62procedure TCoffeineBeverageWithHook.PrepareRecipe;
 63begin
 64  BoilWater;
 65  Brew;
 66  PourInCup;
 67  if CustomerWantsCondiments then
 68    AddCondiments;
 69end;
 70
 71{ TCoffeeWithHook }
 72
 73procedure TCoffeeWithHook.AddCondiments;
 74begin
 75  Writeln(‘Add Sugar and Milk‘);
 76end;
 77
 78procedure TCoffeeWithHook.Brew;
 79begin
 80  Writeln(‘Drip Coffee Through Filter‘);
 81end;
 82
 83function TCoffeeWithHook.CustomerWantsCondiments: Boolean;
 84var
 85  Answer: string;
 86begin
 87  Answer := GetUserInput;
 88  if LowerCase(Answer) = ‘y‘ then
 89    Result := True
 90  else
 91    Result := False;
 92end;
 93
 94function TCoffeeWithHook.GetUserInput: string;
 95var
 96  Answer: string;
 97begin
 98  Answer := ‘‘;
 99  Writeln(‘Would You Like Milk And Sugar With Your Coffee (y / n)? ‘);
100  Readln(Answer);;
101  if Answer = ‘‘ then
102    Result := ‘no‘;
103  Result := Answer;
104end;
105
106{ TTeaWithHook }
107
108procedure TTeaWithHook.AddCondiments;
109begin
110  Writeln(‘Add Lemon‘);
111end;
112
113procedure TTeaWithHook.Brew;
114begin
115  Writeln(‘Steeping the Tea‘);
116end;
117
118function TTeaWithHook.CustomerWantsCondiments: Boolean;
119var
120  Answer: string;
121begin
122  Answer := GetUserInput;
123  if LowerCase(Answer) = ‘y‘ then
124    Result := True
125  else
126    Result := False;
127end;
128
129function TTeaWithHook.GetUserInput: string;
130var
131  Answer: string;
132begin
133  Answer := ‘‘;
134  Writeln(‘Would You Like Lemon With Your Tea (y / n)? ‘);
135  Readln(Answer);
136  if Answer = ‘‘ then
137    Result := ‘no‘;
138  Result := Answer;
139end;
140
141end.
142

 1
 2{《HeadFirst设计模式》之模板方法模式 }
 3{ 客户端                           }
 4{ 编译工具: Delphi7.0              }
 5{ E-Mail : [email protected]      }
 6
 7program pCoffeineBeverageWithHook;
 8
 9{$APPTYPE CONSOLE}
10
11uses
12  SysUtils,
13  uCoffeineBeverageWithHook in ‘uCoffeineBeverageWithHook.pas‘;
14
15var
16  CoffeeHook: TCoffeeWithHook;
17  TeaHook   : TTeaWithHook;
18  
19begin
20  CoffeeHook := TCoffeeWithHook.Create;
21  TeaHook    := TTeaWithHook.Create;
22
23  Writeln(‘Making Coffee‘);
24  CoffeeHook.PrepareRecipe;
25
26  Writeln(‘Making Tea‘);
27  TeaHook.PrepareRecipe;
28
29  FreeAndNil(CoffeeHook);
30  FreeAndNil(TeaHook);
31
32  Readln;
33end.

运行结果：