Lammps设计模式分析

lammps设计模式分析

问题：为什么main函数中，对son->daughterPlus的调用可以改变daughter中的值？

#include <iostream>


class Pointers
{
public:
    class Son *&son;
    class Daughter *&daughter;
    Pointers(class Father *father);
    virtual ~Pointers(){}
};

class Son:protected Pointers
{
public:
    Son(Father *father):Pointers(father){}
    ~Son(){}
    void daughterPlus();
};

class Daughter:protected Pointers
{
public:
    long a;

    Daughter(Father *father):Pointers(father){a=0;}
    ~Daughter(){}
};

void Son::daughterPlus(){
    daughter->a++;
}

class Father
{
public:
    Son *son;
    Daughter *daughter;
    Father(){
        son=new Son(this);
        daughter=new Daughter(this);
    }

    ~Father();
};

Pointers::Pointers(class Father *father): son(father->son),daughter(father->daughter){}

int main(){

    Father *f=new Father();
    // output:0
    std::cout<<f->daughter->a<<std::endl;
    f->son->daughterPlus();
    // output:1
    std::cout<<f->daughter->a<<std::endl;
    return 0;

}

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先看pointer类，这个类声明的时候还没有后面的类，所以他的子类成员变量定义的时候要加class，也可以先声明了后面再定义，这么写：

class Son;
class Daughter;
class Father;
class Pointers
{
public:
    Son *&son;
    Daughter *&daughter;
    Pointers(Father *father);
    virtual ~Pointers(){}
};

然后仔细看这个son跟daughter，继承于pointer，pointer里面放着的正是它们两个的指针引用，所以在son的函数里面可以直接调用daughter的变量。也就是说，son里面有两个指针的引用，一个指向自己，另一个指向daughter，同理daughter也是。

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结构图

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执行

为什么son可以调用daughterPlus()可以将daughter里面的变量a++？

    f->son->daughterPlus();
    //f->son没问题，f里面有son这个指针
    //son->daughterPlus()也没问题，daughterPlus是son的一个成员函数

问题在daughterPlus()里面：

class Son:protected Pointers
{
public:
    Son(Father *father):Pointers(father){}
    ~Son(){}
    void daughterPlus();
};

void Son::daughterPlus(){
    daughter->a++;
}

实际上是这么访问的：