Transform to Nothing if field is empty string
|:: (Monad m, MonadSnap n)|
|=> (n (Maybe a) -> HeistT n m b)|
Function for generating a splice from an optional default value calculated at runtime.
|-> (ByteString -> n (Maybe a))|
Function for retrieving the form default by ID.
|-> HeistT n m b|
Constructs a generalized edit form splice that looks up an ID param
specified by the
by attribute. You might use this splice as follows:
If you don't specify the
by attribute, the default is