Exam App - serializers.py

from rest_framework import serializers

from quiz.models import Quiz, Sitting, Question


class QuestionSerializer(serializers.HyperlinkedModelSerializer):
    """
    Serializer for Question model
    """
    figure = serializers.ImageField(use_url=True)
    content = serializers.CharField()

    class Meta:
        model = Question
        fields = ('figure', 'content',)
        read_only_fields = ('figure', 'content',)


class QuizSerializer(serializers.HyperlinkedModelSerializer):
    """
    Serializer for Quiz model
    """
    title = serializers.CharField(max_length=60)
    description = serializers.CharField(allow_blank=True)
    success_text = serializers.CharField(allow_blank=True)
    fail_text = serializers.CharField(allow_blank=True)
    pass_mark = serializers.IntegerField()

    class Meta:
        model = Quiz
        fields = (
            'title', 'description', 'success_text', 'fail_text',
            'pass_mark',
        )
        read_only_fields = (
            'title', 'description', 'success_text', 'fail_text',
            'pass_mark',
        )


class SittingSerializer(serializers.ModelSerializer):
    """
    Serializer for Sitting model
    """
    user = serializers.HyperlinkedRelatedField(
        view_name='account-detail', read_only=True
    )
    quiz = QuizSerializer()
    question_list = serializers.SerializerMethodField()
    incorrect_questions = serializers.SerializerMethodField()

    class Meta:
        model = Sitting
        fields = ('user', 'quiz', 'question_list', 'incorrect_questions',)
        read_only_fields = ('user', 'quiz', 'question_list', 'incorrect_questions',)

    def _get_questions_from_ids(self, question_list):
        """
        This method accepts a list of question Ids as an argument and returns
        a corresponding list of serialized Questions.
        """
        questions = Sitting.objects.filter(id__in=question_list)
        return map(lambda question: QuestionSerializer(question), questions)

    def get_question_list(self, obj):
        """
        Returns the list of serialized question objects in question_list

        :param obj: Object being serialized, i.e., Sitting object
        """
        return self._get_questions_from_ids(obj.question_list.split(','))

    def get_incorrect_questions(self, obj):
        """
        Returns list of incorrect questions in serialized form

        :param obj: Object being serialized, i.e., Sitting object
        """
        return self._get_questions_from_ids(obj.incorrect_questions.split(','))