cpp_design_learning/builder.cpp

//构造器模式
//构造器严格意义上来说不能算一个单独的设计模式，更多的是对各种组件的构造方式的封装

#include<vector>
#include<iostream>
#include<string>

//将一个类的构造函数进行封装，使得只能用特定的API才能构造对象（和后面的工厂有一些交叉的地方）

class data            //一个最简单的组件
{
private:
    int datas;
public:
    data(int n):datas(n){}
    void print()
    {
        std::cout<<datas<<std::endl;
    }
};

//最简单的构造器（对对应对象的构造函数的封装）
class basic_biulder
{
private:
    std::vector<data> elenment;
public:
    void builder_data(int n)
    {
        elenment.emplace_back(data(n));
    }
    void print()
    {
        for(auto i:elenment)
        {
            i.print();
        }
    }
};


//流式构造器
class builder
{
private:
    std::vector<data> elenment;
public:
    builder& builder_data(int n)
    {
        elenment.emplace_back(data(n));
        return *this;
    }
    builder& print()
    {
        for(auto i:elenment)
        {
            i.print();
        }
        return *this;
    }
};





//组合构造器
//当然能不这么做尽量不要，结构乱七八糟的
class Personbuilder;
class Personbuilderbase;
class PersonbuilderAddress;

class person                      //被构造的数据
{
    std::string address;
    std::string name;
    std::string post_code;
    std::string city;
    int age;
    person(){}
    friend Personbuilder;                  //只有设置为友元才能访问构造函数
    friend PersonbuilderAddress;
public:
    static Personbuilder create();
};

class Personbuilderbase
{
protected:
    person& p;
    explicit Personbuilderbase(person& data):p(data){}
public:
    operator person()                    //类型转换运算符
    {
       return std::move(p);
    }
    PersonbuilderAddress lives()const;

};

class Personbuilder:public Personbuilderbase
{
    person p;
public:
    Personbuilder():Personbuilderbase(p){}

};

Personbuilder person::create()
{
    return Personbuilder();
}




class PersonbuilderAddress:public Personbuilderbase
{
private:
    using self=PersonbuilderAddress;
public:
    explicit PersonbuilderAddress(person& data):Personbuilderbase(data){}
    self& at(std::string address){
        this->p.address=std::move(address);
        return *this;
    }
    //其余的赋值函数可以写在下面
};

PersonbuilderAddress Personbuilderbase::lives() const
{
    return PersonbuilderAddress(p);
}


int main()
{
    //简单构造器
    basic_biulder test_1;
    test_1.builder_data(1);
    test_1.builder_data(2);
    test_1.builder_data(3);
    test_1.builder_data(4);
    test_1.print();


    //流式构造器
    builder test_2;
    test_2.builder_data(1).builder_data(2).builder_data(3).builder_data(4).print();    //能通过流式方法调用

    //组合构造器
    person data=person::create().lives().at("hello");
}