[#bsl-unordered_map-0bf-at-0e]
= xref:bsl.adoc[bsl]::xref:bsl/unordered_map-0bf.adoc[unordered_map<basic_string<char>, Json, TransparentHash, TransparentEqualTo>]::at
:relfileprefix: ../../
:mrdocs:

Return a reference providing modifiable access to the mapped‐value associated with the specified `key`, if such an entry exists; otherwise throw `std::out_of_range` exception. Note that this method is not exception‐neutral.

== Synopsis

Declared in `<bslstl_unorderedmap.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:bsl/add_lvalue_reference-040/type.adoc[add_lvalue_reference<Json>::type]
at(xref:bsl/unordered_map-0bf/key_type.adoc[key_type] const& key);
----


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