插入对象作为键无法编译？

Question

我在编译时遇到了麻烦.我不明白编译器抛出的错误.一些代码来说明问题如下.

#include <map>

using namespace std;

class Thing
{
public:
    Thing(int n):val(n) {}

    bool operator < (const Thing& rhs) const
    {
        return val < rhs.val;
    }

    int getVal() { return val; }

private:
    int val;
};


int main(int argc, char* argv[])
{
    std::map<Thing, int> mymap;
    Thing t1(1);
    Thing t2(10);
    Thing t3(5);

    mymap[t1] = 1; // OK

    mymap.insert(t1); // Compile error
}

现在编译错误消息:

test.cpp:在函数'int main(int,char**)'中:test.cpp:34:错误:没有用于调用'std :: map,std :: allocator >> :: insert(Thing&)的匹配函数'/usr/include/c++/4.4/bits/stl_map.h:499:注意:候选者是:std :: pair,std :: _ Select1st>,_ Compare,typename _Alloc :: rebind> :: other> :: iterator, bool> std :: map <_Key,_Tp,_Compare,_Alloc> :: insert(const std :: pair&)[with _Key = Thing,_Tp = int,_Compare = std :: less,_Alloc = std :: allocator>] /usr/include/c++/4.4/bits/stl_map.h:539:注意:typename std :: _ Rb_tree <_Key,std :: pair,std :: _ Select1st>,_ Compare,typename _Alloc :: rebind> :: other> :: iterator std :: map <_Key,_Tp,_Compare,_Alloc> :: insert(typename std :: _ Rb_tree <_Key,std :: pair,std :: _ Select1st>,_Compare,typename _Alloc :: rebind> ::other> :: iterator,const std :: pair&)[with _Key = Thing,_Tp = int,_Compare = std :: less,_Alloc = std :: allocator>]

那是什么意思？我需要在Thing中定义另一个方法或运算符来进行编译吗？

Answer 1

您需要mymap.insert(std::pair<Thing,int>(t1,x));,x您要映射到的值在哪里t1.