[#BloombergLP-bslstl-HashTable-09-emplaceIfMissing]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::xref:BloombergLP/bslstl/HashTable-09.adoc[HashTable<UnorderedMapKeyConfiguration<basic_string<char> const, pair<basic_string<char> const, Json>>, TransparentHash, TransparentEqualTo, allocator<pair<basic_string<char> const, Json>>>]::emplaceIfMissing
:relfileprefix: ../../../
:mrdocs:

Insert into this hash‐table a newly‐created `ValueType` object, constructed by forwarding the specified (variable number of) `arguments` to the corresponding constructor of `ValueType`, if a key equivalent to that of the newly‐created object does not already exist in this hash‐table. Return the address of the (possibly newly created and inserted) element in this hash table whose key is equivalent to that of an object created from `arguments`. Load `true` into the specified `isInsertedFlag` if a new value was inserted, and `false` if an equivalent key was already present. If this hash‐table contains more than one element with an equivalent key, return the first such element (from the contiguous sequence of elements having a matching key). Additional buckets are allocated, as needed, to preserve the invariant `loadFactor <= maxLoadFactor`. If this function tries to allocate a number of buckets larger than can be represented by this hash‐table's `SizeType`, a `std::length_error` exception is thrown. This method requires that the `ValueType` defined in the (template parameter) type `KEY_CONFIG` be `emplace‐constructible` into this hash‐table from `arguments` (see {Requirements on `KEY_CONFIG`});

== Synopsis

Declared in `<bslstl_hashtable.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class... Args>
xref:BloombergLP/bslalg/BidirectionalLink.adoc[bslalg::BidirectionalLink]*
emplaceIfMissing(
    bool* isInsertedFlag,
    Args&&... arguments);
----


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