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