Creating-Value-Generators.md

Parameters that are included within an exploration (both at the exploration level and the interactive widget level) must each specify both a value generator and an [[object type|Creating-Objects]]. The object type specifies the type of the parameter, while the value generator is responsible (via its generate_value function) for providing an object of the given type when the widget runs. For example, it might simply return a copy of an object given to it (Copier), or it might randomly select an object from a given list (RandomSelector).

Let's suppose you want to create a new value generator called MyValueGenerator (though in practice you should use a more descriptive name).

1. In extensions/value_generators/models/generators.py add a class MyValueGenerator that derives from value_generators_domain.BaseValueGenerator. It should contain a generate_value function that takes the customization_args provided by the widget for the parameter in question, and returns an object of the type the widget specifies for this parameter.
2. In `extensions/value_generators/models/generators_test.py add tests for your class.
3. In extensions/value_generators/templates/, add a file my_value_generator.html that will be used to display the form for editing parameters. The html from the relevant object's template will have been automatically compiled into a object-editor html tag which you should use here.
4. Add a companion MyValueGenerator.js javascript file.