xblock-utils: Various utilities for XBlocks

These are a collection of useful utility functions, test base classes and documentation shared by many XBlocks. (Especially those of edx-solutions.)

To test the utilities, run:

make test

To get a coverage report, use:

tox -- --cover-html

StudioEditableXBlockMixin

from xblockutils.studio_editable import StudioEditableXBlockMixin

This mixin will automatically generate a working studio_view form that allows content authors to edit the fields of your XBlock. To use, simply add the class to your base class list, and add a new class field called editable_fields, set to a tuple of the names of the fields you want your user to be able to edit.

@XBlock.needs("i18n")
class ExampleBlock(StudioEditableXBlockMixin, XBlock):
    ...
    mode = String(
        display_name="Mode",
        help="Determines the behaviour of this component. Standard is recommended.",
        default='standard',
        scope=Scope.content,
        values=('standard', 'crazy')
    )
    editable_fields = ('mode', 'display_name')

That's all you need to do. The mixin will read the optional display_name, help, default, and values settings from the fields you mention and build the editor form as well as an AJAX save handler.

If you want to validate the data, you can override validate_field_data(self, validation, data) and/or clean_studio_edits(self, data) - see the source code for details.

Supported field types:

• Boolean: field_name = Boolean(display_name="Field Name")
• Float: field_name = Float(display_name="Field Name")
• Integer: field_name = Integer(display_name="Field Name")
• String: field_name = String(display_name="Field Name")
• String (multiline): field_name = String(multiline_editor=True, resettable_editor=False)
• String (html): field_name = String(multiline_editor='html', resettable_editor=False)

Any of the above will use a dropdown menu if they have a pre-defined list of possible values.

• List of unordered unique values (i.e. sets) drawn from a small set of possible values: field_name = List(list_style='set', list_values_provider=some_method)
  • The List declaration must include the property list_style='set' to indicate that the List field is being used with set semantics.
  • The List declaration must also define a list_values_provider method which will be called with the block as its only parameter and which must return a list of possible values.
• Rudimentary support for Dict, ordered List, and any other JSONField-derived field types
  • list_field = List(display_name="Ordered List", default=[])
  • dict_field = Dict(display_name="Normal Dict", default={})

Supported field options (all field types):

• values can define a list of possible options, changing the UI element to a select box. Values can be set to any of the formats defined in the XBlock source code:

  • A finite set of elements: [1, 2, 3]

  • A finite set of elements where the display names differ from the values:

    [
        {"display_name": "Always", "value": "always"},
        {"display_name": "Past Due", "value": "past_due"},
    ]
    

  • A range for floating point numbers with specific increments: {"min": 0 , "max": 10, "step": .1}

  • A callable that returns one of the above. (Note: the callable does not get passed the XBlock instance or runtime, so it cannot be a normal member function)

• values_provider can define a callable that accepts the XBlock instance as an argument, and returns a list of possible values in one of the formats listed above.

• resettable_editor - defaults to True. Set False to hide the "Reset" button used to return a field to its default value by removing the field's value from the XBlock instance.

Basic screenshot:

StudioContainerXBlockMixin

from xblockutils.studio_editable import StudioContainerXBlockMixin

This mixin helps to create XBlocks that allow content authors to add, remove, or reorder child blocks. By removing any existing author_view and adding this mixin, you'll get editable, re-orderable, and deletable child support in Studio. To enable authors to add arbitrary blocks as children, simply override author_edit_view and set can_add=True when calling render_children - see the source code. To restrict authors so they can add only specific types of child blocks or a limited number of children requires custom HTML.

An example is the mentoring XBlock:

SeleniumXBlockTest

from xblockutils.base_test import SeleniumXBlockTest

This is a base class that you can use for writing Selenium integration tests that are hosted in the XBlock SDK (Workbench).

Here is an example:

class TestStudentView(SeleniumXBlockTest):
    """
    Test the Student View of MyCoolXBlock
    """
    def setUp(self):
        super(TestStudentView, self).setUp()
        self.set_scenario_xml('<mycoolblock display_name="Test Demo Block" field2="hello" />')
        self.element = self.go_to_view("student_view")

    def test_shows_field_2(self):
        """
        The xblock should display the text value of field2.
        """
        self.assertIn("hello", self.element.text)

StudioEditableBaseTest

from xblockutils.studio_editable_test import StudioEditableBaseTest

This is a subclass of SeleniumXBlockTest that adds a few helper methods useful for testing the studio_view of any XBlock using StudioEditableXBlockMixin.

child_isinstance

from xblockutils.helpers import child_isinstance

If your XBlock needs to find children/descendants of a particular class/mixin, you should use

child_isinstance(self, child_usage_id, SomeXBlockClassOrMixin)

rather than calling

``isinstance(self.runtime.get_block(child_usage_id), SomeXBlockClassOrMixin)``.

On runtimes such as those in edx-platform, child_isinstance is orders of magnitude faster.

XBlockWithSettingsMixin

This mixin provides access to instance-wide XBlock-specific configuration settings. See [wiki page](https://github.com/edx/xblock-utils/wiki/Settings-and-theme-support#accessing-xblock-specific-settings) for details

ThemableXBlockMixin

This mixin provides XBlock theming capabilities built on top of XBlock-specific settings. See [wiki page](https://github.com/edx/xblock-utils/wiki/Settings-and-theme-support#theming-support) for details