If a key equivalent to the specified key already exists in this unordered_map, assign the specified obj to the value associated with that key, and return a pair containing an iterator referring to the existing item and false. Otherwise, insert into this map a newly-created value_type object, constructed from (std::forward<KEY>(key), std::forward<BDE_OTHER_TYPE>(obj)...)), and return a pair containing an iterator referring to the newly-created entry and true.
Declared in <bslstl_unorderedmap.h>
template<class BDE_OTHER_TYPE>
pair<iterator, bool>
insert_or_assign(
BloombergLP::bslmf::MovableRef<KEY> key,
BDE_OTHER_TYPE&& obj);