Mapping a pair to a struct - c++

Question

There's some code I've written which I have trouble with, but I've tried to write a simplified version of it to possibly reproduce the error I'm encountering:
#include <iostream>
#include<bits/stdc++.h>
using namespace std;
struct test{
float y;
};
typedef pair<int, int> intpair;
map<intpair, test> mp;
void func(test &obj){
obj.y = 23.5;
}
int main () {
test* obj = new test;
auto key = make_pair(1,1);
mp.insert(key, obj);
func(*obj);
//cout << *(obj->y);
delete obj;
return 0;
}
What I would like to do is map a pair to a custom struct test that I have created. I get the following error:
main.cpp: In function ‘int main()’:
main.cpp:22:22: error: no matching function for call to ‘std::map, test>::insert(std::pair&, test*&)’
mp.insert(key, obj);
^
In file included from /usr/include/c++/6/map:61:0,
from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:81,
from main.cpp:2:
/usr/include/c++/6/bits/stl_map.h:731:7: note: candidate: std::pair, std::_Select1st >, _Compare, typename __gnu_cxx::__alloc_traits<_Allocator>::rebind >::other>::iterator, bool> std::map<_Key, _Tp, _Compare, _Alloc>::insert(const value_type&) [with _Key = std::pair; _Tp = test; _Compare = std::less >; _Alloc = std::allocator, test> >; typename std::_Rb_tree<_Key, std::pair, std::_Select1st >, _Compare, typename __gnu_cxx::__alloc_traits<_Allocator>::rebind >::other>::iterator = std::_Rb_tree_iterator, test> >; std::map<_Key, _Tp, _Compare, _Alloc>::value_type = std::pair, test>]
insert(const value_type& __x)
^~~~~~
/usr/include/c++/6/bits/stl_map.h:731:7: note: candidate expects 1 argument, 2 provided
/usr/include/c++/6/bits/stl_map.h:739:9: note: candidate: template std::pair, std::_Select1st >, _Compare, typename __gnu_cxx::__alloc_traits<_Allocator>::rebind >::other>::iterator, bool> std::map<_Key, _Tp, _Compare, _Alloc>::insert(_Pair&&) [with _Pair = _Pair; = ; _Key = std::pair; _Tp = test; _Compare = std::less >; _Alloc = std::allocator, test> >]
insert(_Pair&& __x)
^~~~~~
/usr/include/c++/6/bits/stl_map.h:739:9: note: template argument deduction/substitution failed:
main.cpp:22:22: note: candidate expects 1 argument, 2 provided
mp.insert(key, obj);
^
In file included from /usr/include/c++/6/map:61:0,
from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:81,
from main.cpp:2:
/usr/include/c++/6/bits/stl_map.h:752:7: note: candidate: void std::map<_Key, _Tp, _Compare, _Alloc>::insert(std::initializer_list >) [with _Key = std::pair; _Tp = test; _Compare = std::less >; _Alloc = std::allocator, test> >]
insert(std::initializer_list<value_type> __list)
^~~~~~
/usr/include/c++/6/bits/stl_map.h:752:7: note: candidate expects 1 argument, 2 provided
/usr/include/c++/6/bits/stl_map.h:781:7: note: candidate: std::map<_Key, _Tp, _Compare, _Alloc>::iterator std::map<_Key, _Tp, _Compare, _Alloc>::insert(std::map<_Key, _Tp, _Compare, _Alloc>::const_iterator, const value_type&) [with _Key = std::pair; _Tp = test; _Compare = std::less >; _Alloc = std::allocator, test> >; std::map<_Key, _Tp, _Compare, _Alloc>::iterator = std::_Rb_tree_iterator, test> >; std::map<_Key, _Tp, _Compare, _Alloc>::const_iterator = std::_Rb_tree_const_iterator, test> >; std::map<_Key, _Tp, _Compare, _Alloc>::value_type = std::pair, test>]
insert(const_iterator __position, const value_type& __x)
^~~~~~
/usr/include/c++/6/bits/stl_map.h:781:7: note: no known conversion for argument 1 from ‘std::pair’ to ‘std::map, test>::const_iterator {aka std::_Rb_tree_const_iterator, test> >}’
/usr/include/c++/6/bits/stl_map.h:792:9: note: candidate: template std::map<_Key, _Tp, _Compare, _Alloc>::iterator std::map<_Key, _Tp, _Compare, _Alloc>::insert(std::map<_Key, _Tp, _Compare, _Alloc>::const_iterator, _Pair&&) [with _Pair = _Pair; = ; _Key = std::pair; _Tp = test; _Compare = std::less >; _Alloc = std::allocator, test> >]
insert(const_iterator __position, _Pair&& __x)
^~~~~~
/usr/include/c++/6/bits/stl_map.h:792:9: note: template argument deduction/substitution failed:
main.cpp:22:22: note: cannot convert ‘key’ (type ‘std::pair’) to type ‘std::map, test>::const_iterator {aka std::_Rb_tree_const_iterator, test> >}’
mp.insert(key, obj);
^
In file included from /usr/include/c++/6/map:61:0,
from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:81,
from main.cpp:2:
/usr/include/c++/6/bits/stl_map.h:807:9: note: candidate: template void std::map<_Key, _Tp, _Compare, _Alloc>::insert(_InputIterator, _InputIterator) [with _InputIterator = _InputIterator; _Key = std::pair; _Tp = test; _Compare = std::less >; _Alloc = std::allocator, test> >]
insert(_InputIterator __first, _InputIterator __last)
^~~~~~
/usr/include/c++/6/bits/stl_map.h:807:9: note: template argument deduction/substitution failed:
main.cpp:22:22: note: deduced conflicting types for parameter ‘_InputIterator’ (‘std::pair’ and ‘test*’)
mp.insert(key, obj);
Also, I'm sure that I'm going wrong in the way I access my obj's member y (cout statement commented out); How do I go about resolving these issues?

Answer 1

There are no overload of std::map::insert that takes a key and a value.
You can use operator[] to add a new element:
mp[key] = *obj;
Or std::map::insert_or_assign since C++17:
mp.insert_or_assign(key, *obj);
Another point is that type of obj is test* while the type of values of the map mp has type test. The pointer should be dereferenced (like my examples above) or the type of values should be changed to pointers to do this insertion.