django nested models field access

Question

Here's the scenario:

I have a Student Model with subject field connected with Many-to-Many relationship to Subject Model

class Student(models.Model):
    (...)
    subject = models.ManyToManyField(Subject)

In Subject Model i have a program field connected with Many-to-Many relationship to Programs Model. Subject Model got also CharField name.

class Subject(models.Model):
    (...)
    program = models.ManyToManyField(Programs)

In Programs Model i have a field:

class Programs(models.Model):
    name = models.CharField(max_length=40)
    (...)

Django creates additional table for many-to-many fields. In my application I create (with form) a Program and Subject corresponding to Program. Then i create some Students and choose some subjects. How can i access program name field (Student.objects.all()) and display what program name Student is using ?
Is it possible, or i need to create additional fields in Student Model connected with Many-to-Many relationships with Program Model ?

Answer 1

Am I right in thinking that you want to return a list of the program names for the programs belonging to each subject in student.subject?

If so you could use this as a method of the Student model:

def get_program_names(self)
    programs = []
    for subject in self.subjects:
        programs += [program.name for program in subject.program]
    return programs

It sounds from your question, however, that you expect only one program name to be returned. if this is the case then maybe you should replace your manyToMany fields with ForeignKey fields, which give a one to one relationship between two models, meaning that this method should work:

def get_program_name(self):
    return self.subject.program.name

(either way, there is no reason you should have to create a direct link between your student model and the program model, unless you wish to reduce the number of database calls, in which case you could add a field to Student which is updated with the latest program name or similar.)

I hope that I haven't misunderstood your question.