Formulator Field - Override

Description

Sometimes you'd like a field property to be dynamic instead of just a value filled in in the Edit tab of the field. If you fill in the name of an override method for a property in the Override tab, that method will be called whenever you (or the code) asks for the value of that property using get_value(). Properties which are overridden are shown between square brackets ([ and ]) in the main Edit tab, and the value of the property in the edit tab will be ignored. To stop using an override for a particular property, remove the method name in the override tab.

An override method should return an object of the same type as the property field would return after validation. For instance, an override method for a StringField would return a simple string, for an IntegerField it would return an integer, and for a CheckBoxField it would return true or false (or something that can be interpreted that way).

Example

A good example of the use of the override tab is the items property of a ListField; frequently you may want to get these items from elsewhere, for instance from a database. In this case you would fill in the name of the override method for items that retrieves the right data.

The right data in this case is that which validation of the builtin field ListTextArea would return. This is a list of tuples, one tuple for each element. Each tuple consists of two strings; the name that should be displayed to the user for that item, and the actual value that will be submitted.

This for instance is a Python script random_numbers that will return ten random numbers as the elements:

      # random_numbers
      import random
      result = []
      for i in range(10):
        number = random.randint(0, 100)
        tuple = str(number), str(number)
        result.append(tuple)
      return result