建造者模式的定義將一個複雜對象的構建與它的表示分離,使得同樣的構建過程可以創建不同的表示(DP)。《大話設計模式》舉了一個很好的例子——建造小人,一共需建造6個部分,頭部、身體、左右手、左右腳。與工廠模式不同,建造者模式是在導向者的控制下一步一步構造產品的。建造小人就是在控制下一步步構造出來的。創建者模式可以能更精細的控制構建過程,從而能更精細的控制所得產品的內部結構。下面給出建造者模式的UML圖,以建造小人爲實例。
對於客戶來說,只需知道導向者就可以了,通過導向者,客戶就能構造複雜的對象,而不需要知道具體的構造過程。下面給出小人例子的代碼實現。
- class Builder
- {
- public:
- virtual void BuildHead() {}
- virtual void BuildBody() {}
- virtual void BuildLeftArm(){}
- virtual void BuildRightArm() {}
- virtual void BuildLeftLeg() {}
- virtual void BuildRightLeg() {}
- };
- //構造瘦人
- class ThinBuilder : public Builder
- {
- public:
- void BuildHead() { cout<<"build thin body"<<endl; }
- void BuildBody() { cout<<"build thin head"<<endl; }
- void BuildLeftArm() { cout<<"build thin leftarm"<<endl; }
- void BuildRightArm() { cout<<"build thin rightarm"<<endl; }
- void BuildLeftLeg() { cout<<"build thin leftleg"<<endl; }
- void BuildRightLeg() { cout<<"build thin rightleg"<<endl; }
- };
- //構造胖人
- class FatBuilder : public Builder
- {
- public:
- void BuildHead() { cout<<"build fat body"<<endl; }
- void BuildBody() { cout<<"build fat head"<<endl; }
- void BuildLeftArm() { cout<<"build fat leftarm"<<endl; }
- void BuildRightArm() { cout<<"build fat rightarm"<<endl; }
- void BuildLeftLeg() { cout<<"build fat leftleg"<<endl; }
- void BuildRightLeg() { cout<<"build fat rightleg"<<endl; }
- };
- //構造的指揮官
- class Director
- {
- private:
- Builder *m_pBuilder;
- public:
- Director(Builder *builder) { m_pBuilder = builder; }
- void Create(){
- m_pBuilder->BuildHead();
- m_pBuilder->BuildBody();
- m_pBuilder->BuildLeftArm();
- m_pBuilder->BuildRightArm();
- m_pBuilder->BuildLeftLeg();
- m_pBuilder->BuildRightLeg();
- }
- };
- class Builder
- {
- public:
- virtual void BuildHead() {}
- virtual void BuildBody() {}
- virtual void BuildLeftArm(){}
- virtual void BuildRightArm() {}
- virtual void BuildLeftLeg() {}
- virtual void BuildRightLeg() {}
- };
- //構造瘦人
- class ThinBuilder : public Builder
- {
- public:
- void BuildHead() { cout<<"build thin body"<<endl; }
- void BuildBody() { cout<<"build thin head"<<endl; }
- void BuildLeftArm() { cout<<"build thin leftarm"<<endl; }
- void BuildRightArm() { cout<<"build thin rightarm"<<endl; }
- void BuildLeftLeg() { cout<<"build thin leftleg"<<endl; }
- void BuildRightLeg() { cout<<"build thin rightleg"<<endl; }
- };
- //構造胖人
- class FatBuilder : public Builder
- {
- public:
- void BuildHead() { cout<<"build fat body"<<endl; }
- void BuildBody() { cout<<"build fat head"<<endl; }
- void BuildLeftArm() { cout<<"build fat leftarm"<<endl; }
- void BuildRightArm() { cout<<"build fat rightarm"<<endl; }
- void BuildLeftLeg() { cout<<"build fat leftleg"<<endl; }
- void BuildRightLeg() { cout<<"build fat rightleg"<<endl; }
- };
- //構造的指揮官
- class Director
- {
- private:
- Builder *m_pBuilder;
- public:
- Director(Builder *builder) { m_pBuilder = builder; }
- void Create(){
- m_pBuilder->BuildHead();
- m_pBuilder->BuildBody();
- m_pBuilder->BuildLeftArm();
- m_pBuilder->BuildRightArm();
- m_pBuilder->BuildLeftLeg();
- m_pBuilder->BuildRightLeg();
- }
- };
客戶的使用方式:
- int main()
- {
- FatBuilder thin;
- Director director(&thin);
- director.Create();
- return 0;
- }
- int main()
- {
- FatBuilder thin;
- Director director(&thin);
- director.Create();
- return 0;
- }
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