[#boost-urls-params_encoded_base-find-00]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/params_encoded_base.adoc[params_encoded_base]::find
:relfileprefix: ../../../
:mrdocs:


Find a matching key

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_encoded_base.hpp#L431[boost/url/params_encoded_base.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/params_encoded_base/iterator.adoc[iterator]
find(
    xref:boost/urls/params_encoded_base/iterator.adoc[iterator] from,
    xref:boost/urls/pct_string_view.adoc[pct_string_view] key,
    xref:boost/urls/ignore_case_param.adoc[ignore_case_param] ic = {}) const noexcept;
----

== Description


This function examines the parameters        in the container to find a match for        the specified key, which may contain        percent escapes.        The comparison is performed as if all        escaped characters were decoded first.

The search starts at `from`        and proceeds forward until either the        key is found or the end of the range is        reached, in which case `end()` is        returned.


=== Example

[,cpp]
----
url_view u( "?First=John&Last=Doe" );

assert( u.encoded_params().find( "first" ) != u.encoded_params().find( "first", ignore_case ) );
----

=== Complexity

Linear in `this‐>buffer().size()`.


=== Exception Safety

Exceptions thrown on invalid input.



== Exceptions


|===
| Name | Thrown on

| `system_error`
| `key` contains an invalid percent‐encoding.


|===

== Return Value


an iterator to the param



== Parameters


|===
| Name | Description

| *from*
| The position to begin the            search from. This can be `end()`.


| *key*
| The key to match.        By default, a case‐sensitive        comparison is used.


| *ic*
| An optional parameter. If        the value xref:boost/urls/ignore_case.adoc[ignore_case] is passed        here, the comparison is        case‐insensitive.


|===



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