Adds an element constructed in place.
template<class ValTy>
pair<iterator, bool> emplace(ValTy&& val);
Parameters
Parameter |
Description |
ValTy |
The in-place constructor argument type. |
val |
Value to insert. |
Remarks
The member function determines whether an element X exists in the sequence whose key has equivalent ordering to that of val. If not, it constructs such an element X with val. The function then determines the iterator where that designates X. If an insertion occurred, the function returns std::pair(where, true). Otherwise, it returns std::pair(where, false).
If an exception is thrown during the insertion, the container is left unaltered and the exception is rethrown.
Example
// std_tr1__unordered_map__unordered_map_emplace.cpp
// compile with: /EHsc
#include <unordered_map>
#include <iostream>
#include <string>
int main()
{
using namespace std;
unordered_map<int, string> c1;
pair<int, string> is1(1, "a");
c1.emplace(move(is1));
cout << "After the emplace insertion, c1 contains:" << endl
<< " " << c1.begin()->first
<< " => " << c1.begin()->second
<< endl;
return (0);
}
After the emplace insertion, c1 contains: 1 => a
Requirements
Header: <unordered_map>
Namespace: std