From cppreference.com
template<class...Args>iteratoremplace(Args&&...args);(since C++11)Inserts a new element into the container constructed in-place with the given args.
The constructor of the new element (i.e. std::pair<constKey,T>) is called with exactly the same arguments as supplied to emplace, forwarded via std::forward<Args>(args)....
Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations.
No iterators or references are invalidated.
Parameters
args - arguments to forward to the constructor of the element Return value
An iterator to the inserted element.
Exceptions
If an exception is thrown for any reason, this function has no effect (
strong exception safety guarantee
).
Complexity
Logarithmic in the size of the container.
Example
Run this code
#include<iostream>#include<string>#include<utility>#include<map>intmain(){std::multimap<std::string,std::string>m;// uses pair's move constructorm.emplace(std::make_pair(std::string("a"),std::string("a")));// uses pair's converting move constructorm.emplace(std::make_pair("b","abcd"));// uses pair's template constructorm.emplace("d","ddd");// emplace with duplicate key m.emplace("d","DDD");// uses pair's piecewise constructorm.emplace(std::piecewise_construct,std::forward_as_tuple("c"),std::forward_as_tuple(10,'c'));for(constauto&p:m)std::cout<<p.first<<" => "<<p.second<<'\n';}Output:
a => a b => abcd c => cccccccccc d => ddd d => DDD See also
(C++11)
constructs elements in-place using a hint
(public member function)
inserts in-place if the key does not exist, does nothing if the key exists
(public member function)
inserts elements or nodes(since C++17)
(public member function)