[#boost-urls-params_base-const_iterator]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/params_base.adoc[params&lowbar;base]::const&lowbar;iterator
:relfileprefix: ../../../
:mrdocs:


A Bidirectional iterator to a query parameter

== Synopsis


Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_base.hpp#L98[boost&sol;url&sol;params&lowbar;base&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
using const&lowbar;iterator = xref:boost/urls/params_base/iterator.adoc[iterator];
----

== Description


Objects of this type allow iteration        through the parameters in the query&period;        Any percent&hyphen;escapes in returned strings        are decoded first&period;        The values returned are read&hyphen;only&semi;        changes to parameters must be made        through the container instead, if the        container supports modification&period;

The strings produced when iterators are        dereferenced belong to the iterator and        become invalidated when that particular        iterator is incremented, decremented,        or destroyed&period;

[NOTE]
The implementation may use temporary,        recycled storage to store decoded        strings&period; These iterators are meant        to be used ephemerally&period; That is, for        short durations such as within a        function scope&period; Do not store        iterators with static storage        duration or as long&hyphen;lived objects&period;





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