c++设计与编程之包含关系(包容关系)
在使用包含内容的时候，对于表示类X的对象，存在着两种主要的可选方式：
1生命一个类型为X的成员2生命一个类型为X*或者X&的成员
如果指针值绝不改变，那么除了效率问题和写构造函数，析构函数的方式之外，这些选择方案是完全等价的：
class X{
public:
X(int);
};
class C{
X a;
X *p;
X &r;
public:
C(int i,intj,int k):a(i),p(new X(j)),r(*new X(k)){}
~C(){delete p;delete &r;}
}1包含指针

#include<iostream>#include<string>using namespace std;class Person{public: Person(string name,int age){  this->name=name;  this->age=age; } Person(){} virtual void show(){  cout<<name<<" "<<age; }private: string name; int age;};class Student{public: Student(string name,int age,string number1):p(new Person(name,age)),number(number1){} Student(){} void show(){  p->show();  cout<<" "<<number<<endl; }private: string number; Person *p;};int main(){ Student s("zhang",22,"091150"); s.show(); system("pause"); return 0;}

#include<iostream>#include<string>using namespace std;class Person{public: Person(string name,int age){  this->name=name;  this->age=age; } Person(){} virtual void show(){  cout<<name<<" "<<age; }private: string name; int age;};class Student{public: Student(string name,int age,string number1):p(name,age),number(number1){} Student(){} void show(){  p.show();  cout<<" "<<number<<endl; }private: string number; Person p;};int main(){  Student s("zhang",22,"091150"); s.show(); system("pause"); return 0;}

#include<iostream>#include<string>using namespace std;class Person{public: Person(string name,int age){  this->name=name;  this->age=age; } Person(){} virtual void show(){  cout<<name<<" "<<age; }private: string name; int age;};class Student{public: Student(string name,int age,string number1):number(number1),p(*new Person(name,age)){} Student():p(*new Person()){}  //这步不能少，一定得初始化 void show(){  p.show();  cout<<" "<<number<<endl; } private: string number; Person &p; };int main(){  Student s("zhang",22,"091150"); s.show(); system("pause"); return 0;}