Question

I want to create a website for students with django.

I have learning_plan with n subjects

When I create a student I want to choose an existing learning_plan and have automatic all the subjects that the learning_plan has, also I want to have exam_grades different for each student.

What I’ve done so far:

class Subject(models.Model):
    name = models.CharField(max_length=60)

    def __unicode__(self):
        return self.name

class LearningPlan(models.Model):
    name = models.CharField(max_length=60)
    subjects = models.ManyToManyField(Subject, through='Exam')

    def __unicode__(self):
        return self.name

class Student(models.Model):
    name = models.CharField(max_length=60)
    learning_plan = models.ForeignKey(LearningPlan)

    def __unicode__(self):
        return self.name


class Exam(models.Model):
    subject = models.ForeignKey(Subject)
    learning_plan = models.ForeignKey(LearningPlan)
    exam_grade = models.IntegerField()

I know what I want I do not know how to do it. I want to have a plan with Subjects: Subject1, Subject2, Subject3 … and when I add a new student I select a plan and see all the subjects from the grade associated to the student and to can add exam_grade to each of the Subjects (Subeject1, Subject2, Subject3 …) and the grades for the same subject to be different for different students. I do not know how to implement this.

Answer 1

If you have a student and what to get his (her) subjects, use this:

student.learning_plan.subjects.all()

Exam grades are simple too, but it’s better to add related_name first:

class Exam(models.Model):
    subject = models.ForeignKey(Subject)
    learning_plan = models.ForeignKey(LearningPlan, related_name='exams')
    exam_grade = models.IntegerField()

Now you can get student’s exams:

student.learning_plan.exams.all()

And if you want to add an exam, it’s still simple:

new_exam = Exam.objects.create(subject=some_subject, learning_plan=some_lp, exam_grade=98)
student.learning_plan.exams.add(new_exam)