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：www.
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
[cpp] view plaincopyprint?
#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;
}

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2包含对象
[cpp] view plaincopyprint?
#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;
}
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3包含引用
[cpp] view plaincopyprint?
#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;
}
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特别注意包含指针和引用指针，要new一个，最好加多一个析构函数delete删除一个，包含引用的时候，别忘了初始化。