gistfile1.py

### Code for passing through edit pages

# Handle a PUT request.
def put(self, *args):
	BaseController.put(self, *args)
	
	# Form is a dictionary with elements like
	#     property_name: list_of_validators.
	form = self.model.form
	
	# Models must have a form. There are validators like
	# required, optional, etc. so that all properties can
	# be validated.
	assert form is not None
	
	# Call self.request.get() for all given inputs. Returns
	# a dictionary (property_name: user_input).
	data = self.get_data(*form.keys())
	
	try:
	  # Get the entity, given its id.
	  # NOTE: The first argument is the resource id.
		resource = self.get_resource(list(args)[0])
		assert resource is not None
		
		for name, value in data.items():
		  
		  # The value must be different from the existing one.
			if value != getattr(resource, name):
				try:
				  
				  # Iterate through all the validators for the given field.
					for validator in form[name]:
					  
					  # NOTE: Validators return a value, possibly coerced.
						value = validator(value)
					
					# If all validation passes for the given field, the new value
					# will successfully replace the old one.
					setattr(resource, name, value)
				
				# If validation fails, an IOError is raised, so if the
				# new value is bad, the old value remains unchanged.
				except IOError: pass
		
		resource.put()
		
		# Resource.link() is the URL to its show page.
		return self.redirect(resource.link())
	
	# If the resource does not exist, the user probably wants
	# the new page instead of this one. (Or should this be self.error(404)?)
	except AssertionError:
		self.redirect('/%ss/new' % self._name)