Delphi实现简单工厂模式（转载）

计算器的功能实现
实现工厂设计模式
通过面向对象的思想，进行设计，所用的编程思想为对象的三大特性：封装，继承，多态
通过实现一个简单的 计算器的功能（输入两个数，进行加，减，乘，除）

思想思路：
1.设计虚拟父类;
2.子类继承父类
3. 通过虚拟方法，进行进行重载
4.工厂类，实例化对象，采用多态

 

  1 unit uOperation;
  2 
  3 interface
  4 
  5 uses Classes, inifiles;
  6 
  7 type
  8 {基础类}
  9 TOperation = class(Tobject)
 10 private
 11 FNumberA: Double;
 12 FNumberB: Double;
 13 public
 14 function GetResult: double; virtual; abstract;
 15 property NumberA: Double read FNumberA write FNumberA;
 16 property NumberB: Double read FNumberB write FNumberB;
 17 constructor create;
 18 destructor Destroy; override;
 19 end;
 20 
 21 {加法}
 22 TAdd = class(TOperation)
 23 public
 24 function GetResult: double; override;
 25 end;
 26 
 27 {减法}
 28 TSub = class(Toperation)
 29 public
 30 function GetResult: double; override;
 31 end;
 32 
 33 {乘法}
 34 TMultiple = class(TOperation)
 35 public
 36 function GetResult: double; override;
 37 end;
 38 
 39 {除法}
 40 TDev = class(TOperation)
 41 public
 42 function GetResult: Double; override;
 43 end;
 44 
 45 {工厂类}
 46 
 47 TOperationFactory = class
 48 private
 49 FOpMap: TStringHash;
 50 public
 51 
 52 {可以 GetOperation 定义为类方法，这样就不用创建TOperationFactory 对象，可以直接使用
 53 
 54 TOperationFactory.GetOperation 但是在本例子中，由于要创建 FOpMap，所有不能定义 类方法，根据情况灵活应用，还有
 55 
 56 简单工厂模式，返回值是父类型}
 57 function GetOperation(Op: string): TOperation;
 58 constructor create;
 59 destructor Destroy; override;
 60 
 61 end;
 62 
 63 implementation
 64 
 65 { TOperation }
 66 
 67 constructor TOperation.create;
 68 begin
 69 
 70 end;
 71 
 72 destructor TOperation.Destroy;
 73 begin
 74 
 75 inherited;
 76 end; 
 77 
 78 { TAdd }
 79 
 80 function TAdd.GetResult: double;
 81 begin
 82 result := FNumberA + FNumberB;
 83 end;
 84 
 85 { TSub }
 86 
 87 function TSub.GetResult: double;
 88 begin
 89 result := FNumberA - FNumberB;
 90 end;
 91 
 92 { TMultiple }
 93 
 94 function TMultiple.GetResult: double;
 95 begin
 96 Result := FNumberA * FNumberB;
 97 end;
 98 
 99 { TDev }
100 
101 function TDev.GetResult: Double;
102 begin
103 Result := 0;
104 if FNumberB <> 0 then
105 Result := FNumberA / FNumberB;
106 
107 end;
108 
109 { TOperationFactory }
110 
111 constructor TOperationFactory.create;
112 begin
113 FOpMap := TStringHash.Create;
114 FOpMap.Add('+', 1);
115 FOpMap.Add('-', 2);
116 FOpMap.Add('*', 3);
117 FOpMap.Add('/', 4);
118 end;
119 
120 destructor TOperationFactory.Destroy;
121 begin
122 FOpMap.Free;
123 inherited;
124 end;
125 
126 function TOperationFactory.GetOperation(Op: string): TOperation;
127 begin
128 result := nil;
129 case FOpMap.ValueOf(Op) of
130 1: result := TAdd.create;
131 2: result := TSub.create;
132 3: result := TMultiple.create;
133 4: result := TDev.create;
134 end;
135 end;
136 end.
137 
138 {使用}
139 
140 unit Unit1;
141 
142 interface
143 
144 uses
145 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
146 Dialogs, StdCtrls;
147 
148 type
149 TForm1 = class(TForm)
150 Button1: TButton;
151 Edit1: TEdit;
152 Edit2: TEdit;
153 Edit3: TEdit;
154 Label1: TLabel;
155 Label2: TLabel;
156 Label3: TLabel;
157 Label4: TLabel;
158 Edit4: TEdit;
159 procedure Button1Click(Sender: TObject);
160 private
161 { Private declarations }
162 public
163 { Public declarations }
164 end;
165 
166 var
167 Form1: TForm1;
168 
169 implementation
170 
171 uses uOperation;
172 
173 {$R *.dfm}
174 
175 procedure TForm1.Button1Click(Sender: TObject);
176 var
177 op: TOperation;
178 OpFact: TOperationFactory;
179 begin
180 OpFact := TOperationFactory.create;
181 
182 op := OpFact.GetOperation(Edit4.Text);
183 try
184 if op = nil then exit;
185 op.NumberA := strtointdef(Edit1.Text, -1);
186 op.NumberB := strtointdef(Edit2.Text, -1);
187 edit3.Text := FloatToStr(op.GetResult);
188 finally
189 OPFact.Free;
190 OP.Free;
191 end;
192 end;
193 
194 end.

 

 

posted @ 2012-05-26 11:38  世界之窗  阅读(491)  评论(0)    收藏  举报