extending-dialogs.py

#!python2
# coding: utf-8

# https://forum.omz-software.com/topic/2462/dialogs-module-extending-it

# Yeah, some sort of data validation for dialogs.form_dialog() would definitely be useful.

# Here's an idea for a relatively simple implementation that wouldn't require changes in the dialogs module itself (though it duplicates some code from there). It's not as granular as you might want (e.g. it's not possible to validate input while typing), but it's probably good enough for a lot of use cases. It's basically just an additional validator parameter, which should be a function/callable. When the Done button in the dialog is tapped, this function gets the (preliminary) result of the dialog, can inspect it, and it should return a list of fields (keys) that are invalid for whatever reason. These fields are then highlighted in red, and the dialog remains on screen.

# Extension of dialogs.form_dialog() that supports simple data validation

from __future__ import print_function
import dialogs
import collections
import ui

class ValidatingFormDialogController (dialogs._FormDialogController):
	def done_action(self, sender):
		if callable(self.validator):
			invalid_keys = self.validator(self.values)
			if invalid_keys:
				for i, (title, fields) in enumerate(self.sections):
					for j, field in enumerate(fields):
						cell = self.cells[i][j]
						if field['key'] in invalid_keys:
							cell.text_label.text_color = 'red'
						else:
							cell.text_label.text_color = None
				return
		if self.shield_view:
			self.dismiss_datepicker(None)
		else:
			ui.end_editing()
			self.was_canceled = False
			self.container_view.close()
			
def form_dialog(title='', fields=None, sections=None, done_button_title='Done', validator=None):
	if not sections and not fields:
		raise ValueError('sections or fields are required')
	if not sections:
		sections = [('', fields)]
	if not isinstance(title, str) and not isinstance(title, unicode):
		raise TypeError('title must be a string')
	for section in sections:
		if not isinstance(section, collections.Sequence):
			raise TypeError('Sections must be sequences (title, fields)')
		if len(section) < 2:
			raise TypeError('Sections must have 2 or 3 items (title, fields[, footer]')
		if not isinstance(section[0], str) and not isinstance(section[0], unicode):
			raise TypeError('Section titles must be strings')
		if not isinstance(section[1], collections.Sequence):
			raise TypeError('Expected a sequence of field dicts')
		for field in section[1]:
			if not isinstance(field, dict):
				raise TypeError('fields must be dicts')
	c = ValidatingFormDialogController(title, sections, done_button_title=done_button_title)
	c.validator = validator
	c.container_view.present('sheet')
	c.container_view.wait_modal()
	c.container_view = None
	if c.was_canceled:
		return None
	return c.values
	
# --- DEMO:

def validate_form(values):
	# This gets called before the dialog is dismissed via 'Done'.
	# It should return a list of keys that failed to pass validation.
	# If no invalid keys are returned, the dialog is closed as usual,
	# otherwise, the invalid fields are highlighted in red.
	invalid = []
	# Title must be 'Mr', 'Mrs', or 'Ms':
	if values.get('title') not in ['Mr', 'Mrs', 'Ms']:
		invalid.append('title')
	# Name must not be empty:
	if len(values.get('name')) < 1:
		invalid.append('name')
	# 'Accept Terms' must be checked:
	if not values.get('terms'):
		invalid.append('terms')
	return invalid
	
def main():
	fields = [{'type': 'text', 'key': 'title', 'title': 'Title (Mr/Mrs/Ms)'}, {'type': 'text', 'key': 'name', 'title': 'Name'}, {'type': 'switch', 'key': 'terms', 'title': 'Accept Terms'}]
	r = form_dialog('Test', fields, validator=validate_form)
	print(r)
	
if __name__ == '__main__':
	main()