如何在C ++中对匿名对象使用operator =? [英] How to use operator= with anonymous objects in C++?

问题描述

我有一个带有重载运算符的类:

I have a class with an overloaded operator:

IPAddress& IPAddress::operator=(IPAddress &other) {
    if (this != &other) {
        delete data;
        this->init(other.getVersion());
        other.toArray(this->data);
    }
    return *this;
}

当我尝试编译时:

IPAddress x;
x = IPAddress(IPV4, "192.168.2.10");

我收到以下错误:

main.cc: In function ‘int main()’:
main.cc:43:39: error: no match for ‘operator=’ in ‘x = IPAddress(4, ((const std::string&)(& std::basic_string<char>(((const char*)"192.168.2.10"), ((const std::allocator<char>&)((const std::allocator<char>*)(& std::allocator<char>())))))))’
IPAddress.h:28:20: note: candidate is: IPAddress& IPAddress::operator=(IPAddress&)

但是，这两个都可以正常工作(尽管它们对我没有任何作用):

However, these two work fine (though they don't serve me any purpose):

IPAddress x;
IPAddress(IPV4, "192.168.2.10") = x;

-

IPAddress x;
x = *(new IPAddress(IPV4, "192.168.2.10"));

这是怎么回事?我是否对赋值运算符的工作方式有误?

What's going on? Am I assuming something incorrect about the way the assignment operator works?

推荐答案

赋值运算符的右侧应为const IPAddress&.

The right side of the assignment operator should take a const IPAddress&.

临时对象可以绑定到const引用，但不能绑定到非const引用.这就是x = IPAddress(IPV4, "192.168.2.10");无法正常工作的原因.

Temporary objects can be bound to const references, but not to non-const references. This is why x = IPAddress(IPV4, "192.168.2.10"); doesn't work.

IPAddress(IPV4, "192.168.2.10") = x;之所以起作用，是因为在临时对象上调用成员函数是合法的.

IPAddress(IPV4, "192.168.2.10") = x; works because it is legal to invoke member functions on temporary objects.

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