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= cowboy_constraints:nonempty(3)
== Name
cowboy_constraints:nonempty - Non-empty constraint
== Description
Constraint functions implement a number of different operations.
[source,erlang]
----
nonempty(forward | reverse, <<>>) -> {error, empty}
----
Reject empty values.
[source,erlang]
----
nonempty(forward | reverse, Bin) -> {ok, Bin}
Bin :: binary()
----
Accept any other binary values.
[source,erlang]
----
nonempty(format_error, Error) -> HumanReadable
Error :: {empty, Bin}
HumanReadable :: iolist()
----
Generate a human-readable error message.
== Arguments
Arguments vary depending on the operation. Constraint
functions always take the operation type as first argument,
and the value as second argument.
== Return value
The return value varies depending on the operation.
== Changelog
* *2.0*: Interface modified to allow for a variety of operations.
* *1.0*: Constraint introduced.
== Examples
This function is not meant to be called directly.
== See also
link:man:cowboy_constraints(3)[cowboy_constraints(3)],
link:man:cowboy_constraints:int(3)[cowboy_constraints:int(3)],
link:man:cowboy_router(3)[cowboy_router(3)],
link:man:cowboy_req:match_cookies(3)[cowboy_req:match_cookies(3)],
link:man:cowboy_req:match_qs(3)[cowboy_req:match_qs(3)]
|
