C++ 重载cout

#include "iostream"
using namespace std;

class Complex
{
private:
 int a;
 int b;
 friend ostream& operator<<(ostream &out, Complex &c1);  // ostream是系统自带cout的类型

public:
 Complex(int a = 0, int b = 0)
 {
  this->a = a;
  this->b = b;
 }
 void printCom()
 {
  cout<<a<<"+"<<b<<"i"<<endl;
 }
};


ostream  &operator<<(ostream &out, Complex &c1)    //进来后又出去
{
 cout<<"12345,上山打老虎"<<endl;
 cout<<c1.a<<"+"<<c1.b<<"i"<<endl;
 return out;
}

//1操作符重载，首先是通过函数实现的。
int main()
{
 Complex c1(1, 2), c2(3, 4); 
 int a = 10;
 //char *p = "abc";
 //cout<<a<<endl;  //正确
 //cout<<c1<<endl;  //正确
 
 //cout<<c1<<"链式编程测试"<<endl;   //不自定义<<则错误 ，没法打印<<错误自定义版（链式结构）
 //operator<<(cout,c1),cout是左操作数
 //链式编程，c1<<"***" 等价于void<<"***";错误

 //函数返回值当左值的时候，需要返回一个对象的引用， 没有方法在cout类里面添加函数operator<<，只能通过全局函数实现.
 //友元的真正用武之地
 cout.operator<<(c1);
 return 0;
}