C++ using的多种用法

1、引入命名空间

using namespace std;using std::cout;

2、引入基类成员

class Base{public:void func(){cout << "Base::func()" << endl;}};class Derived : public Base{public:using Base::func;void func(int x){cout << "Derived::func(x)" << x << endl;}};int main(){Derived d;d.func();//Base::func()d.func(1);//Derived::func(x)return 0;}

3、取别名

//给类型取别名using type = int;type x = 10;//给FormatItem类型的智能指针取名为ptrusing ptr = shared_ptr;templateclass A{public://给模板类型取别名using value_type = T;//T func(){}value_type func(){}private://T x;value_type x;}