Remove link between Problem and MultipleChoiceOption

Each MultiplechoiceOption is linked to a Problem, but this link is redundant since each Problem can be linked to a FeedbackOption, which is already linked to a Problem.

changed due date to May 18, 2019

added Database Priority A Ruben To Do labels

There is a problem with the proposed change in this issue.

Currently the API call GET /exams/<id>, which fetches one exam, returns a rather large JSON object. The JSON response currently looks like this

{
            'id': exam_id,
            'name': exam.name,
            'submissions': submissions,
            'problems': [
                {
                    'id': prob.id,
                    'name': prob.name,
                    'feedback': [
                        {
                            'id': fb.id,
                            'name': fb.text,
                            'description': fb.description,
                            'score': fb.score,
                            'used': len(fb.solutions)
                        }
                        for fb
                        in prob.feedback_options  # Sorted by fb.id
                    ],
                    'page': prob.widget.page,
                    'widget': {
                        'id': prob.widget.id,
                        'name': prob.widget.name,
                        'x': prob.widget.x,
                        'y': prob.widget.y,
                        'width': prob.widget.width,
                        'height': prob.widget.height,
                    },
                    'graded': any([sol.graded_by is not None for sol in prob.solutions])
                } for prob in exam.problems  # Sorted by prob.id
            ],
            'widgets': [
                {
                    'id': widget.id,
                    'name': widget.name,
                    'x': widget.x,
                    'y': widget.y,
                } for widget in exam.widgets  # Sorted by widget.id
            ],
            'finalized': exam.finalized,
        }

Ideally, after for example "widget", you would want to use a JSON notation that constructs an array of MultipleChoiceOptions with a notation like

[for mc_option in problem.mc_options]

If the relationship between MultipleChoiceOption and Problem is removed, this would not be possible. This means that some query has to be written manually before the JSON is constructed, which may not be as efficient.

One way to resolve this issue is to add a relationship between FeedbackOption and MultipleChoiceOption (see also #35 (closed)), but then a notation like

[for mc_option in feedback_option.mc_options]

would be very much redundant since the MultipleChoiceOptions are unique to a problem and not to a FeedbackOption.

A comment from Hugo:

If you add a relationship field mc_option to FeedbackOption using db.relationship, you can do something like the following: mc_option in [fb_option.mc_option for fb_option in problem.feedback_options if fb_option.mc_option]

You could even add a hybrid property mc_options to Problem, see https://docs.sqlalchemy.org/en/13/orm/extensions/hybrid.html

mentioned in merge request !12 (merged)

Fixed in !12 (merged)

closed