【c++11关键字】 explicit

/*
 * c++11关键字
 * explicit
 * 拒绝隐式转换
 * 小鱼号的代码日志
*/
#include <QCoreApplication>
#include <iostream>
using namespace  std;
struct A
{
    A(int){}
    A(int,int){}
    operator int() const {return 0;}
};
struct B
{
    explicit B(int){}
    explicit B(int,int){}
    explicit operator int() const {return 0;}
};
void handleA(A a)
{
}
void handleB(B a)
{
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    A a1 = 1;
    //B b1 = 1;  ///BAD
    A a2(2);
    B b2(2);
    A a3 = {4,5};
    //B b3 = {4,5}; ///BAD
    int na1 = a1;
    //int nb1 = b1;    ///BAD
    int na2 = static_cast<int>(a1);
    //int nb2 = static_cast<int>(b1); ///BAD
    A a4 = (A)1;
    B b4 = (B)1; //OK
    handleA(a1);
    handleA(1);
    handleB(b2);
    //handleB(2);///BAD
    return a.exec();
}