&#39;std::string {aka std::basic_string 赋值中的不兼容类型<char> }&#39; 到

Question

int main()
{

std::string my_string= "16657";
std::map<std::string, std::string[2]> m_msg_int;
std::string arrId[2];
arrId[0] = "ABC";
arrId[1] = "XYZ/CDE";
m_msg_int[my_string] = arrId[2];
std::cout<<"MSGID"<<msgId[0]<<endl;

 }

incompatible types in assignment of 'std::string {aka std::basic_string}' to 'std::map, std::basic_string [2]>::mapped_type {aka std::basic_string [2]}'

Answer 1

In line

m_msg_int[my_string] = arrId[2];

you are accessing the array arrId out of bounds because it has size of 2 and reading arrId[2] causes undefined behavior. Even if you wouldn't access out of bounds

m_msg_int[my_string]

is a reference to an array of strings and

arrId[2]

is a string. Probably you are trying to assign

m_msg_int[my_string] = arrId;

but in C++ you can't assign a basic array to a basic array. You should use std::array for this

#include <array>
#include <map>
#include <string>

int main()
{
    std::string my_string= "16657";
    std::map<std::string, std::array<std::string, 2>> m_msg_int;
    std::array<std::string, 2> arrId;
    arrId[0] = "ABC";
    arrId[1] = "XYZ/CDE";
    m_msg_int[my_string] = arrId;
    //std::cout<<"MSGID"<<msgId[0]<<endl;
}

Answer 2

You assign a std::string to a array of std::string .

m_msg_int[my_string] = arrId;

Now we assign a array of std::string to our map.

NOTE : Array index range is n to n-1 . And you can't do this:

m_msg_int[my_string] = arrId[2];

Because arrId have 2 element, But index 2 means third element.