[#boost-urls-params_ref-set-01]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/params_ref.adoc[params_ref]::set
:relfileprefix: ../../../
:mrdocs:


Set a value

== Synopsis


Declared in `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/params_ref.hpp#L910[boost/url/params_ref.hpp]>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/params_base/iterator.adoc[iterator]
set(
    core::string_view key,
    core::string_view value,
    xref:boost/urls/ignore_case_param.adoc[ignore_case_param] ic = {});
----

== Description


This function performs one of two        actions depending on the value of        `this‐>contains( key, ic )`.

* If key is contained in the view        then one of the matching elements has
        its value changed to the specified value.        The remaining elements with a matching
        key are erased. Otherwise,
* If 
`key`
 is not contained in the        view, then the function apppends the
        param 
`{ key, value }`
.

All iterators are invalidated.


=== Example

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

u.params().set( "id", "none" );

assert( u.params().count( "id" ) == 1 );
----

=== Postconditions

[,cpp]
----
this->count( key, ic ) == 1 && this->find( key, ic )->value == value
----

=== Complexity

Linear in `this‐>url().encoded_query().size()`.


=== Exception Safety

Strong guarantee.        Calls to allocate may throw.

Set a value

This function performs one of two        actions depending on the value of        `this‐>contains( key, ic )`.

* If key is contained in the view        then one of the matching elements has
        its value changed to the specified value.        The remaining elements with a matching
        key are erased. Otherwise,
* If 
`key`
 is not contained in the        view, then the function apppends the
        param 
`{ key, value }`
.

All iterators are invalidated.


=== Example

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

u.params().set( "id", "none" );

assert( u.params().count( "id" ) == 1 );
----

=== Postconditions

[,cpp]
----
this->count( key, ic ) == 1 && this->find( key, ic )->value == value
----

=== Complexity

Linear in `this‐>url().encoded_query().size()`.


=== Exception Safety

Strong guarantee.        Calls to allocate may throw.



== Return Value


An iterator to the appended        or modified element.



== Parameters


|===
| Name | Description

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


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


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


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


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


| *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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