创建型模式-生成器(builder)

生成器

将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示.

实例

main.cc:

/*design_patterns:"builder"In the production of mobile phones, for example, now the mobile phone manufacturers will launch high-end, midrange, low-end configuration version, the basic configuration of most of them, only a few key parts are different, it is very suitable for the use of Builder modehigh-end :835 Processor,5.5 inch Panel,8G Memory.midrange :820 Processor,4.7 inch Panel,4G Memory.low-end  :810 Processor,4.0 inch Panel,2G Memory.*/#include "builder.h"#include "high_phone_builder.h"#include "normal_phone_builder.h"#include "low_phone_builder.h"#include "director.h"#include "phone.h"#include <windows.h>#include <iostream>void main(){    //create director    Director *director = new Director();    Builder *high_builder = new HighPhoneBuilder();    director->SetBuilder(high_builder);    //create high-end phone    Phone *high_phone = director->AssemblePhone();    high_phone->ShowConfig();    Builder *normal_builder = new NormalPhoneBuilder();    director->SetBuilder(normal_builder);    //create midrange phone    Phone *normal_phone = director->AssemblePhone();    normal_phone->ShowConfig();    Builder *low_builder = new LowPhoneBuilder();    director->SetBuilder(low_builder);    //create low-end phone    Phone *low_phone = director->AssemblePhone();    low_phone->ShowConfig();    //clear    delete high_builder;    delete normal_builder;    delete low_builder;    delete director;    cout << "ending!" << endl;    system("Pause");}

Director:

//director.h#ifndef HELENDP_SOURCE_DIRECTOR_H_#define HELENDP_SOURCE_DIRECTOR_H_#include "phone.h"#include "builder.h"class Director{public:    Director();    ~Director();    Phone *AssemblePhone();    void SetBuilder(Builder *builder);private:    Builder *builder_;};#endif//director.cc#include "director.h"#include "builder.h"Director::Director(){}Director::~Director(){}Phone *Director::AssemblePhone(){    builder_->AssembleStepOne();    builder_->AssembleStepTwo();    builder_->AssembleStepThree();    return builder_->GetPhone();}void Director::SetBuilder(Builder *builder){    builder_ = builder;}

Builder:

//builder.h#ifndef HELENDP_SOURCE_BUILDER_H_#define HELENDP_SOURCE_BUILDER_H_#include <string>#include "phone.h"using namespace std;class Builder{public:    Builder();    virtual ~Builder();    virtual void AssembleStepOne() = 0;    virtual void AssembleStepTwo() = 0;    virtual void AssembleStepThree() = 0;    virtual Phone* GetPhone() = 0;};#endif//builder.cc#include "builder.h"#include <iostream>using namespace std;Builder::Builder(){}Builder::~Builder(){}

HighPhoneBuilder:

//high_phone_builder.h#ifndef HELENDP_SOURCE_HIGH_PHONE_BUILDER_H_#define HELENDP_SOURCE_HIGH_PHONE_BUILDER_H_#include "builder.h"#include "Phone.h"class HighPhoneBuilder:public Builder{public:    HighPhoneBuilder();    ~HighPhoneBuilder();    void AssembleStepOne();    void AssembleStepTwo();    void AssembleStepThree();    Phone* GetPhone();private:        Phone *phone_;};#endif//high_phone_builder.cc#include "high_phone_builder.h"HighPhoneBuilder::HighPhoneBuilder(){    phone_ = new Phone();}HighPhoneBuilder::~HighPhoneBuilder(){    delete phone_;}void HighPhoneBuilder::AssembleStepOne(){    phone_->AssembleProcessor("SnapDragon835");}void HighPhoneBuilder::AssembleStepTwo(){    phone_->AssembleMemory("8G Memory");}void HighPhoneBuilder::AssembleStepThree(){    phone_->AssemblePanel("5.5 inch panel");}Phone* HighPhoneBuilder::GetPhone(){    return phone_;}

LowPhoneBuilder:

//low_phone_builder.h#ifndef HELENDP_SOURCE_LOW_PHONE_BUILDER_H_#define HELENDP_SOURCE_LOW_PHONE_BUILDER_H_#include "builder.h"#include "phone.h"class LowPhoneBuilder:public Builder{public:    LowPhoneBuilder();    ~LowPhoneBuilder();    void AssembleStepOne();    void AssembleStepTwo();    void AssembleStepThree();    Phone* GetPhone();private:    Phone* phone_;};#endif//low_phone_builder.cc#include "low_phone_builder.h"LowPhoneBuilder::LowPhoneBuilder(){    phone_ = new Phone();}LowPhoneBuilder::~LowPhoneBuilder(){    delete phone_;}void LowPhoneBuilder::AssembleStepOne(){    phone_->AssembleProcessor("SnapDragon810");}void LowPhoneBuilder::AssembleStepTwo(){    phone_->AssembleMemory("2G Memory");}void LowPhoneBuilder::AssembleStepThree(){    phone_->AssemblePanel("4.0 inch panel");}Phone* LowPhoneBuilder::GetPhone(){    return phone_;}

NormalPhoneBuilder:

//normal_phone_builder.h#ifndef HELENDP_SOURCE_NORMAL_PHONE_BUILDER_H_#define HELENDP_SOURCE_NORMAL_PHONE_BUILDER_H_#include "builder.h"#include "phone.h"class NormalPhoneBuilder:public Builder{public:    NormalPhoneBuilder();    ~NormalPhoneBuilder();    void AssembleStepOne();    void AssembleStepTwo();    void AssembleStepThree();    Phone* GetPhone();private:    Phone* phone_;};#endif//normal_phone_builder.cc#include "normal_phone_builder.h"NormalPhoneBuilder::NormalPhoneBuilder(){    phone_ = new Phone();}NormalPhoneBuilder::~NormalPhoneBuilder(){    delete phone_;}void NormalPhoneBuilder::AssembleStepOne(){    phone_->AssembleProcessor("SnapDragon820");}void NormalPhoneBuilder::AssembleStepTwo(){    phone_->AssembleMemory("4G Memory");}void NormalPhoneBuilder::AssembleStepThree(){    phone_->AssemblePanel("4.7 inch panel");}Phone* NormalPhoneBuilder::GetPhone(){    return phone_;}

Phone:

//phone.h#ifndef HELENDP_SOURCE_PHONE_H_#define HELENDP_SOURCE_PHONE_H_#include <string>using namespace std;/*Mobile phone includes processor, memory, panel and other basic configuration*/class Phone{public:    Phone();    ~Phone();    void AssembleProcessor(string processor);    void AssembleMemory(string memory);    void AssemblePanel(string panel);    void ShowConfig();private:    string processor_;    string memory_;    string panel_;    string base_config_;};#endif//phone.cc#include "phone.h"#include <iostream>using namespace std;Phone::Phone(){    base_config_ = "base config";}Phone::~Phone(){}void Phone::AssembleProcessor(string processor){    processor_ = processor;}void Phone::AssembleMemory(string memory){    memory_ = memory;}void Phone::AssemblePanel(string panel){    panel_ = panel;}void Phone::ShowConfig(){    cout << "ShowConfig:" << endl;    cout << base_config_ << endl;    cout << processor_ << endl;    cout << memory_ << endl;    cout << panel_ << endl << endl;}

代码和UML图(EA)工程文件,最后会整理打包上传.

UML类图

结构

• Director(Director):指挥者
• Builder(Builder):抽象建造者
• ConcreteBuilder(HighPhoneBuilder,LowPhoneBuilder,NormalPhoneBuilder):具体建造者
• Product(Phone):产品角色

优点

• 在建造者模式中， 客户端不必知道产品内部组成的细节，将产品本身与产品的创建过程解耦，使得相同的创建过程可以创建不同的产品对象.
• 每一个具体建造者都相对独立，而与其他的具体建造者无关，因此可以很方便地替换具体建造者或增加新的具体建造者， 用户使用不同的具体建造者即可得到不同的产品对象.
• 可以更加精细地控制产品的创建过程 .将复杂产品的创建步骤分解在不同的方法中，使得创建过程更加清晰，也更方便使用程序来控制创建过程.
• 增加新的具体建造者无须修改原有类库的代码，指挥者类针对抽象建造者类编程，系统扩展方便，符合“开闭原则”.

缺点

• 建造者模式所创建的产品一般具有较多的共同点，其组成部分相似，如果产品之间的差异性很大，则不适合使用建造者模式，因此其使用范围受到一定的限制.
• 如果产品的内部变化复杂，可能会导致需要定义很多具体建造者类来实现这种变化，导致系统变得很庞大.