= 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)]