[Twisted-web] freeform and adbapi

Stephan Cieszynski darkblue.mail at gmx.net
Sun Apr 17 16:35:10 MDT 2005

Tommi Virtanen wrote:
> coerce cannot defer. To do that, move your validation into e.g. the
> start of an autocallable and do something like
> def foo(self, ctx, foo, bar):
>     if not valid(foo):
>         raise annotate.ValidateError(
>             {'foo': 'Foo is bad.' },
>             partialForm=ctx.locate(inevow.IRequest).args)
>     ...
> foo = annotate.autocallable(foo)
> where the dict is variablename->errormessage. See ValidateError for
> more.

Sorry, but the following description lead me to use a deferred:

     def coerce(self, val, configurable):
         """Coerce the input 'val' from a string into a value suitable
         for the type described by the implementor. If coercion fails,
         coerce should raise InputError with a suitable error message
         to be shown to the user. 'configurable' is the configurable object
         in whose context the coercion is taking place.

         May return a Deferred.

Your example not working:
First, if 'foo' is a deferred the callback isn't fired at this time and 
validating isn't possible. Second, raising an exception in a 
autocallable like this

def foo(self, ctx, bar):
	def _cb(r):
		if not valid(r):
			raise annotate.ValidateError(...)


take no effect at rendering time and the slot('error') isn't filled with 
our errormessage.


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