cowboy/doc/src/manual/cowboy_req.binding.asciidoc

= cowboy_req:binding(3)

== Name

cowboy_req:binding - Access a value bound from the route

== Description

[source,erlang]
----
binding(Name, Req)          -> binding(Name, Req, undefined)
binding(Name, Req, Default) -> any() | Default

Name    :: atom()
Req     :: cowboy_req:req()
Default :: any()
----

Return the value for the given binding.

== Arguments

Name::

Desired binding name as an atom.

Req::

The Req object.

Default::

Default value returned when the binding is missing.

== Return value

By default the value is a case sensitive binary string, however
constraints may change the type of this value (for example
automatically converting numbers to integer).

== Changelog

* *2.0*: Only the value is returned, it is no longer wrapped in a tuple.
* *1.0*: Function introduced.

== Examples

.Get the username from the path
[source,erlang]
----
%% Route is "/users/:user"
Username = cowboy_req:binding(user, Req).
----

.Get the branch name, with a default
[source,erlang]
----
%% Route is "/log[/:branch]"
Branch = cowboy_req:binding(branch, Req, <<"master">>)
----

== See also

link:man:cowboy_req(3)[cowboy_req(3)],
link:man:cowboy_req:bindings(3)[cowboy_req:bindings(3)],
link:man:cowboy_req:host_info(3)[cowboy_req:host_info(3)],
link:man:cowboy_req:path_info(3)[cowboy_req:path_info(3)],
link:man:cowboy_router(3)[cowboy_router(3)]