[#boost-urls-params_base-get_or]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/params_base.adoc[params_base]::get_or
:relfileprefix: ../../../
:mrdocs:

Return the value for a key or a fallback

== Synopsis

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

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

== Description

This convenience function searches for the first parameter matching `key` and returns its decoded value. If no parameter with the specified key exists, the provided fallback `value` is returned instead. When the key is found but the parameter has no value, an empty string is returned.

== Example

[,cpp]
----
url_view u( "/path?first=John&last=Doe" );
assert( u.params().get_or( "first", "n/a" ) == "John" );
assert( u.params().get_or( "missing", "n/a" ) == "n/a" );
----
== Complexity

Linear in `this‐>buffer().size()`.

== Exception Safety

Calls to allocate may throw.

== Return Value

The decoded value or the fallback.

== Parameters

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

| *key*
| The key to match.
| *value*
| The fallback string returned when no matching key exists. If this parameter is omitted, an empty string is used.
| *ic*
| Optional case‐insensitive compare indicator.
|===


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