没有匹配运算符<<在std :: cout [英] No match for operator << in std::cout

问题描述

我想打印一个向量内的每个元素，如下：

I'm trying to print every element inside a vector like this:

vector<users>::iterator i;

for(i = userlist.begin(); i<userlist.end(); i++)
{
        cout << *i << "\n";
}

然后我得到这样的错误：

Then I'm getting an error like this:

no match for 'operator<<' in 'std::cout << (&i)->__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = users*, _Container = std::vector<users, std::allocator<users> >]()' 

这是我错过的明显吗？

推荐答案

您是否使用此签名定义了一个函数：

Have you defined a function with this signature?:

std::ostream & operator<<(std::ostream &, const users &);

它不是用户的会员功能，可能不是朋友，取决于你。原型应该放在类用户的头文件中，正文应该放在源（.cpp）文件中。我不知道你的用户类是如何定义的，或者你想如何格式化输出，但函数定义应该看起来像这样：

It should not be a member function of users, although it may or may not be a friend, up to you. The prototype should go in the header file of class users, and the body should go in the source(.cpp) file. I have no idea how your users class is defined, or how you would want to format the output, but the function definition should look something like this:

std::ostream & operator<<(std::ostream & os, const users & U)
{
    os << U.some_data_members;
    os << U.and_or_some_member_functions();
    os << whatever;
    return os;
}

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