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


Designate a named argument for a replacement field

== Synopsis


Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/format.hpp#L447[boost&sol;url&sol;format&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;class T&gt;
xref:boost/urls/named_arg.adoc[named&lowbar;arg]&lt;T&gt;
arg(
    core::string&lowbar;view name,
    T const& arg);
----

== Description


Construct a named argument for a format URL    string that contains named replacement fields&period;

The function parameters should be convertible    to an implementation defined type able to    store the name and a reference to any type    potentially used as a format argument&period;


=== Example

The function should be used to designate a named    argument for a replacement field in a format    URL string&period;

[,cpp]
----
assert(format("user/{id}", arg("id", 1)).buffer() == "user/1");
----


== Return Value


A temporary object with reference    semantics for a named argument



== Parameters


|===
| Name | Description

| *name*
| The format argument name


| *arg*
| The format argument value


|===

== See Also


xref:boost/urls/format-02.adoc[format],        xref:boost/urls/format_to-0b.adoc[format&lowbar;to]&period;






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