重载的布尔/字符串歧义 [英] Overloaded Bool/String Ambiguity

问题描述

为什么C ++强制将我传入的字符串文字转换为布尔值而不是字符串?

Why is C++ casting the string literal I pass in as a bool rather than a string?

#include <iostream>

using namespace std;

class A
{
    public:
        A(string v)
        {
            cout << v;
        }

        A(bool v)
        {
            cout << v;
        }
};

int main()
{
    A("hello");
    return 0;
}

输出:1

是因为编译器不够聪明，无法从char *跳转到字符串，而是仅仅假设bool是最接近指针的东西吗?我唯一的选择是制作一个显式的char *构造函数，该构造函数基本上与字符串构造函数完全相同吗?

Is it because the compiler isn't smart enough to make the jump from char * to string and rather just assumes that bool is the closest thing to a pointer? Is my only option to make an explicit char * constructor that basically does the exact same thing as the string constructor?

推荐答案

如果您拥有C ++ 11，则可以使用委托的构造函数:

If you have C++11 you can use a delegating constructor:

A(char const* s) : A(std::string(s)) { }

之所以选择布尔转换构造函数而不是std::string的原因是因为从char const*到bool的转换是标准转换，而到std::string的转换是用户定义的转换.标准转化的排名要高于用户定义的转化.

The reason the boolean converting-constructor is chosen over the one for std::string is because the conversion from char const* to bool is a standard conversion while the one to std::string is a user-defined conversion. Standard conversions have a greater rank than user-defined conversions.

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