C++中using的四大用法总结

请直接看：C++中using的四大用法总结

补充说明：第四点就是为了防止如下错误：

#include <iostream>
using namespace std;
class base
{
public:
    void test()
    {
        cout << "base::test()" << endl;
    }
    void test(double)
    {
        cout << "base::test(double)" << endl;
    }
    void test(int)
    {
        cout << "base::test(int)" << endl;
    }
};
class derived : public base
{
public:
    void test()
    {
        cout << "derived::test()" << endl;
    }
    // using base::test;
};
 
int main(int argc, char **argv)
{
    derived *pb = new derived();
    pb->test(2.4);
    return 0;
}

上述代码会提示：没有函数derived::test(double)

正确代码：

#include <iostream>
using namespace std;
class base
{
public:
void test()
{
cout << "base::test()" << endl;
}
void test(double)
{
cout << "base::test(double)" << endl;
}
void test(int)
{
cout << "base::test(int)" << endl;
}
};
class derived : public base
{
public:
using base::test;
 void test()
{
cout << "derived::test()" << endl;
}
// using base::test;
};

int main(int argc, char **argv)
{
derived *pb = new derived();
pb->test(2.4);
return 0;
}