Django signals post_save update

Question

When the student enrollment record (discount type) is updated the student discount (discount type) is also updated, but what should i do if i want to update the student enrollment record (discount type) using student discount (discount type)

This is my models.py

class studentDiscount(models.Model):
    Students_Enrollment_Records = models.ForeignKey(StudentsEnrollmentRecord, related_name='+',
                                                    on_delete=models.CASCADE, null=True)
    Discount_Type = models.ForeignKey(Discount, related_name='+', on_delete=models.CASCADE, null=True,blank=True)

    @receiver(pre_save, sender=StudentsEnrollmentRecord)
    def get_older_instance(sender, instance, *args, **kwargs):
        try:
            instance._old_instance = StudentsEnrollmentRecord.objects.get(pk=instance.pk)
        except StudentsEnrollmentRecord.DoesNotExist:
            instance._old_instance = None

    @receiver(post_save, sender=StudentsEnrollmentRecord)
    def create(sender, instance, created, *args, **kwargs):
        if not created:
            older_instance = instance._old_instance
            if older_instance.Discount_Type != instance.Discount_Type:

                studentDiscount.objects.filter(
                    Students_Enrollment_Records=instance
                ).delete()
            else:
                return None

        discount = studentDiscount.objects.filter(Discount_Type=instance.Discount_Type)
        if created:
            print("nagsulod")
            studentDiscount.objects.create(
                Students_Enrollment_Records=instance,
                Discount_Type=instance.Discount_Type)
        else:
            studentDiscount.objects.create(
                Students_Enrollment_Records=instance,
                Discount_Type=instance.Discount_Type)

    def __str__(self):
        suser = '{0.Students_Enrollment_Records}'
        return suser.format(self)

class StudentsEnrollmentRecord(models.Model):
    Student_Users = models.ForeignKey(StudentProfile, on_delete=models.CASCADE,null=True)
    School_Year = models.ForeignKey(SchoolYear, related_name='+', on_delete=models.CASCADE, null=True, blank=True)
    Courses = models.ForeignKey(Course, related_name='+', on_delete=models.CASCADE, null=True, blank=True)
    strands = models.ForeignKey(strand, related_name='+', on_delete=models.CASCADE, null=True, blank=True)
    Section = models.ForeignKey(Section, related_name='+', on_delete=models.CASCADE, null=True,blank=True)
    Payment_Type = models.ForeignKey(PaymentType, related_name='+', on_delete=models.CASCADE, null=True)
    Discount_Type = models.ForeignKey(Discount, related_name='+', on_delete=models.CASCADE, null=True,blank=True)
    Education_Levels = models.ForeignKey(EducationLevel, related_name='+', on_delete=models.CASCADE,blank=True,null=True)
    ESC = models.ForeignKey(esc, on_delete=models.CASCADE,null=True,blank=True)
    Remarks = models.TextField(max_length=500,null=True,blank=True)

class Discount(models.Model):
    Code=models.CharField(max_length=500,blank=True)
    Discount_Type=models.CharField(max_length=500,blank=True)
    Remarks=models.TextField(max_length=500,blank=True)
    TuitionFee_Discount_Amount=models.FloatField(null=True,blank=True)
    TuitionFee_Discount_Rate = models.FloatField(null=True,blank=True)
    Miscellaneous_Discount_Amount=models.FloatField(null=True,blank=True)
    Miscellaneous_Discount_Rate = models.FloatField(null=True,blank=True)

if i update the student enrollment record (Discount_Type)

the student discount (discount type) update as well

but when i update the student discount (discount_type)

the student enrollment record (discount type) doesn't update

score 0 · Accepted Answer · answered Jan 24 '20 at 16:29

0

You need to write a signal handler for when the studentDiscount instance is created or updated. You'd need similar methods to studentDiscount.create, but it would need to exist on StudentsEnrollmentRecord and the sender be studentDiscount.

answered Jan 24 '20 at 16:29

schillingt

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Then what should I do mr @schillingt? Can you provide example using my code? – Jan 24 '20 at 17:06
1

No, I think this is a good learning opportunity for you. Your code handles the one direction, now you need to reverse it for the other. I've provided the direction, the implementation is left to you. – schillingt Jan 24 '20 at 17:10

Django signals post_save update

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