:relfileprefix: ../../
[#boost-urls-arg]

== xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::arg


Designate a named argument for a replacement field


=== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/format.hpp#L403[boost/url/format.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
template<class T>
pass:q[_implementation-defined_]
arg(
    core::string_view name,
    T const& arg);
----

=== Description


Construct a named argument for a format URL
string that contains named replacement fields.

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




=== Return Value


An temporary object with reference
semantics for a named argument



=== Parameters

|===
| Name | Description 

| *name*
| 
The argument name

| *arg*
| 
The argument value

|===




=== See Also


xref:boost/urls/format-02.adoc[format]
,
xref:boost/urls/format_to-0b.adoc[format_to]
.