C ++操作符继承和重载 [英] C++ operator inheritance and overloading

问题描述

我有一个基类A和一个派生类B. A和B都定义了[]运算符，但是没有相同的参数类型。仍然，当我尝试对类型B的对象使用[]操作符与A arg C ++没有找到A的def这个。很烦人。什么是规则？

I have a base class A and a derived class B. A and B both define the [] operator but not with the same argument type. Still, when I try to use the [] operator on an object of type B with A arg C++ doesn't find A's def of this. Very annoying. What's the rule?

推荐答案

类B中的运算符隐藏类A中的运算符。一个重载超类中的方法的派生类。如果名称查找在 B 中找到名称匹配，它不会在 A 中查找，即使匹配不能调用 B 中找到的

The operator in class B hides the operator in class A. This is a problem with any method defined in a derived class that overloads a method in a super class. If name lookup finds a name match in B it doesn't look in A, even if the match(s) found in B can't be called.

您需要将其放入B的范围：

You need to bring it into the scope of B:

class X{};
class Y{};

class A {
public:
    auto operator[](X) {};
};

class B : public A {
public:
    using A::operator[]; // <-- you need this
    auto operator[](Y){};
};


int main() {
    A a;
    B b;
    b[X{}]; // OK
    b[Y{}]; // OK
}

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