[#boost-urls-params_encoded_ref-unset]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/params_encoded_ref.adoc[params&lowbar;encoded&lowbar;ref]::unset
:relfileprefix: ../../../
:mrdocs:

Remove the value on an element

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/params_encoded_base/iterator.adoc[iterator]
unset(xref:boost/urls/params_encoded_base/iterator.adoc[iterator] pos) noexcept;
----

== Description

This function removes the value of an element at the specified position&period; After the call returns, `has&lowbar;value` for the element is false&period;

All iterators that are equal to `pos` or come after are invalidated&period;

== Example

[,cpp]
----
url u( "?first=John&last=Doe" );

u.encoded_params().unset( u.encoded_params().begin() );

assert( u.encoded_query() == "first&last=Doe" );
----
== Complexity

Linear in `this&hyphen;&gt;url()&period;encoded&lowbar;query()&period;size()`&period;

== Exception Safety

Throws nothing&period;

== Return Value

An iterator to the element&period;

== Parameters

[cols="1,4"]
|===
|Name|Description

| *pos*
| An iterator to the element&period;
|===


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