:relfileprefix: ../../../
[#boost-urls-params_encoded_ref-set-0d]

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


Set a value


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_encoded_ref.hpp#L879[boost/url/params_encoded_ref.hpp,window=blank_]>`

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

== Description


This function replaces the value of an
element at the specified position.



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

The string passed in must not come
from the element being replaced,
or else the behavior is undefined.

=== Example
[,cpp]
----
url u( "?id=42&id=69" );

u.encoded_params().set( u.encoded_params().begin(), "none" );

assert( u.encoded_query() == "id=none&id=69" );
----

=== Complexity

Linear in `this-&gt;url().encoded_query().size()`.

=== Exception Safety

Strong guarantee.
Calls to allocate may throw.
Exceptions thrown on invalid input.



== Exceptions

|===
| Name | Thrown on

| `system_error`
| 
`value` contains an invalid percent-encoding.

|===


== Return Value


An iterator to the element.



== Parameters

|===
| Name | Description 

| *pos*
| 
An iterator to the element.

| *value*
| 
The value to assign. The
empty string still counts as a value.
That is, `has_value` for the element
is true.

|===