C++构造函数的分类

构造函数的分类：

    无参构造函数

    有参构造函数

    赋值构造函数（拷贝构造函数）

#include<iostream>

using namespace std;

class test

{

public:

          test()

          {

                     m_a = 10;

          }

          test(int a, int b)

          {

                    m_a = a;

                    m_b = b;

          }

          test(int a)

          {

                    m_a = a;

                    m_b = 0;

          }

public:

          int getA()

          {

                    return m_a;

          }

          int getB()

          {

                    return m_b;

          }

private:

          int m_a;

          int m_b;

};

void main()

{

          //test t1;                       //调用无参构造函数

          //cout <<"a="<<t1.getA() << endl;   //输出为10

          test t2(1,2);//1、括号法，调用有参构造函数

          cout << "a1=" << t2.getA() << endl;//输出a=1,b=2

          cout << "b1=" << t2.getB() << endl;

          test t3 = (1, 3);//2,=号法  输出a=1,b=0 

          cout << "a2=" << t3.getA() << endl; //(1, 3)为逗号表达式，整个括号相当于逗号表达式最后一个数的值

          cout << "b2=" << t3.getB() << endl;//所以调用只有一个参数的构造函数

          test t4 = test(2, 8);//3、直接调用构造函数 手动调用构造函数

          cout << "b3=" << t4.getA() << endl;//匿名对象

          cout << "b3=" << t4.getB() << endl;

          system("pause");

}