如何将char*插入map <string,string>？

Question

我有两个单词char*,我想插入它们map<string,string>,因此我尝试了两种方法,但它们没有用 -

第一路 -

#include <iostream>
#include <string>
#include <map>
using namespace std;
void main()
{
    map<string,string> myMap ; 
    char cWord[4] = "abc"; 
    char cValue[4] = "123";
    myMap.insert(cWord,cValue) ; 
}

我收到了一个错误 -

/usr/include/c++/4.4/bits/stl_tree.h: In member function ‘void std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_unique(_II, _II) [with _InputIterator = char*, _Key = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Val = std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _KeyOfValue = std::_Select1st<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, _Compare = std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _Alloc = std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]’:
/usr/include/c++/4.4/bits/stl_map.h:553:   instantiated from ‘void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = char*, _Key = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Tp = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Compare = std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _Alloc = std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]’
testString.cpp:10:   instantiated from here
/usr/include/c++/4.4/bits/stl_tree.h:1324: error: no matching function for call to ‘std::_Rb_tree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::_Select1st<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::_M_insert_unique_(std::_Rb_tree_iterator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, char&)’
/usr/include/c++/4.4/bits/stl_tree.h:1206: note: candidates are: std::_Rb_tree_iterator<_Val> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_unique_(std::_Rb_tree_const_iterator<_Val>, const _Val&) [with _Key = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Val = std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _KeyOfValue = std::_Select1st<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, _Compare = std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _Alloc = std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]

第二路 -

    // same include's as above ..
    map<string,string> myMap ; 
    // char* init ..    
    char cWord[4] = "abc"; 
    char cValue[4] = "123";

    // string ..
    string word(cWord) ; 
    string value(cValue) ; 
    myMap.insert(word,value) ; 

我收到了一个错误 -

error: ‘::main’ must return ‘int’
In file included from /usr/include/c++/4.4/map:60,
                 from testString2.cpp:3:
/usr/include/c++/4.4/bits/stl_tree.h: In member function ‘void std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_unique(_II, _II) [with _InputIterator = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Key = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Val = std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _KeyOfValue = std::_Select1st<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, _Compare = std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _Alloc = std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]’:
/usr/include/c++/4.4/bits/stl_map.h:553:   instantiated from ‘void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Key = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Tp = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Compare = std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _Alloc = std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]’
testString2.cpp:15:   instantiated from here
/usr/include/c++/4.4/bits/stl_tree.h:1323: error: no match for ‘operator++’ in ‘++__first’
/usr/include/c++/4.4/bits/stl_map.h:553:   instantiated from ‘void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Key = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Tp = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Compare = std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, _Alloc = std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >]’
testString2.cpp:15:   instantiated from here
/usr/include/c++/4.4/bits/stl_tree.h:1324: error: no match for ‘operator*’ in ‘*__first’

Answer 1

从文档^1中可以看出map.insert,您需要的重载只需要一个参数.在那里它并不是立即明显的,但它想要一个pair<string, string>包含关键和价值的东西.你可以做,例如:

myMap.insert(make_pair(string(cWord),string(cValue))); 

将其转换char[]为string"动态",pair用它们创建并将其插入地图中; 你不能这样做make_pair(cWord, cValue),因为有没有从隐式转换pair<char *, char *>到pair<string, string>;

不过,在这种情况下,使用operator[]²更容易:

myMap[cWord]=cValue;

请注意,在这里您可以避免string临时构造,因为在此上下文中,允许编译器自动创建它们.

顺便说一句int main,不是void main.

1. 这里有更加精确和最新的C++ 11添加,但恕我直言新手不太清楚.

2. 但请记住,当密钥已经存在时,语义insert和语义operator[]不同:operator[]覆盖,而不insert执行任何操作.