:relfileprefix: ../../../
[#boost-urls-params_encoded_ref-unset]

= xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/params_encoded_ref.adoc[pass:[params_encoded_ref]]::unset


Remove the value on an element


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_encoded_ref.hpp#L832[boost/url/params_encoded_ref.hpp,window=blank_]>`

[source,cpp,subs="verbatim,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.
After the call returns, `has_value`
for the element is false.



All iterators that are equal to
`pos` or come after are invalidated.

=== 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-&gt;url().encoded_query().size()`.

=== Exception Safety

Throws nothing.




== Return Value


An iterator to the element.



== Parameters

|===
| Name | Description 

| *pos*
| 
An iterator to the element.

|===