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

Return true if a matching key exists

== Synopsis

Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_base.hpp#L281[boost&sol;url&sol;params&lowbar;base&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
bool
contains(
    core::string&lowbar;view key,
    xref:boost/urls/ignore_case_param.adoc[ignore&lowbar;case&lowbar;param] ic = &lcub;&rcub;) const noexcept;
----

== Description

This function examines the parameters in the container to find a match for the specified key&period; The comparison is performed as if all escaped characters were decoded first&period;

== Example
[,cpp]
----
assert( url_view( "?first=John&last=Doe" ).params().contains( "first" ) );
----
== Complexity
Linear in `this&hyphen;&gt;buffer()&period;size()`&period;

== Exception Safety
Throws nothing&period;

== Return Value

`true` if a matching key exists&period;

== Parameters

[cols=2]
|===
| Name
| Description
| *key*
| The key to match&period; By default, a case&hyphen;sensitive comparison is used&period;
| *ic*
| An optional parameter&period; If the value xref:boost/urls/ignore_case.adoc[`ignore&lowbar;case`] is passed here, the comparison is case&hyphen;insensitive&period;
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#
