thank you @Chetan the solution does work and I am very grateful!!!!!! On Fri, Nov 13, 2020 at 5:35 PM Chetan Ganji <[email protected]> wrote:
> Im not 100% sure about this :P > > Instead of this - > def save(self, *args, **kwargs): > if self.records.count() <= 0: > for student in self.klass.students.all(): > self.records.create(student=student, status='present') > super(Attendance, self).save(*args, **kwargs) > > > Try with below code - > > def save(self, *args, **kwargs): > super(Attendance, self).save(*args, **kwargs) > if self.records.count() <= 0: > for student in self.klass.students.all(): > self.records.create(student=student, status='present') # separate sql > query i guess for each entry created. > > > There is a diff logic. > > 1. create attendance object. > 2. bulk create AttendanceRecord objects > https://docs.djangoproject.com/en/3.1/ref/models/querysets/#bulk-create > > P.S. both of this operations should happen inside a transaction. > https://docs.djangoproject.com/en/3.1/topics/db/transactions/ > > > Regards, > Chetan Ganji > +91-900-483-4183 > [email protected] > http://ryucoder.in > > > On Fri, Nov 13, 2020 at 4:41 PM DumbaClassics <[email protected]> > wrote: > >> Hello Family may you help. >> >> I am trying to create a School Attendance Module and I have a >> StudentClass table, the Student table, Attendance table and the >> AttendanceRecord table. Here is the code >> >> class StudentClass(models.Model): >> name = models.CharField(max_length=100) >> # stream = models.ForeignKey('Stream', on_delete=models.PROTECT) >> creation_date = models.DateTimeField(auto_now=False, >> auto_now_add=True) >> >> >> def __str__(self): >> return self.name >> >> class Student(models.Model): >> name = models.CharField(max_length=100) >> klass = models.ForeignKey('StudentClass', models.PROTECT, >> related_name='students') >> >> def __str__(self): >> return self.name >> >> class Attendance(models.Model): >> date = models.DateTimeField(auto_now_add=True) >> klass = models.ForeignKey('StudentClass', models.PROTECT, >> related_name='attendances') >> >> def save(self, *args, **kwargs): >> if self.records.count() <= 0: >> for student in self.klass.students.all(): >> self.records.create(student=student, status='present') >> super(Attendance, self).save(*args, **kwargs) >> >> def __str__(self): >> return f"{self.id}, {self.date}" >> >> class AttendanceRecord(models.Model): >> ATTENDANCE_STATUS = [ >> ('present', 'PRESENT'), >> ('absent', 'ABSENT') >> ] >> attendance = models.ForeignKey( >> 'Attendance', >> on_delete=models.SET_NULL, >> null=True, >> blank=True, >> related_name='records' >> ) >> student = models.ForeignKey('Student', on_delete=models.PROTECT) >> status = models.CharField(max_length=100, choices=ATTENDANCE_STATUS) >> >> >> def __str__(self): >> return f"(STUDENT: {self.student}, STATUS: {self.status})" >> >> >> What am I trying to achieve?? >> >> I want to have a situation whereby when I trigger the creation of a >> Attendance instance an Attendance Record linked to that instance is >> generated with the record generating default attendance records for all >> students enrolled in that klass with a default attendance status of present >> which I can get on to edit only for those students who are absent. The >> method I tried for ovveriding the save method didnt work as it generated >> this error ' "unsaved related object '%s'." % field.name >> ValueError: save() prohibited to prevent data loss due to unsaved related >> object 'attendance'.' >> >> I wasnt really confident of that solution anyway. >> >> May you assist me on how best one wld solve such a problem >> >> Thank you in Advance >> >> Dumba >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Django users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-users/2742a034-586d-44a2-872a-5d0c24dc8d70n%40googlegroups.com >> <https://groups.google.com/d/msgid/django-users/2742a034-586d-44a2-872a-5d0c24dc8d70n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/CAMKMUjvhmpEbB4LeEBnYX5-e8LPVb3m7wpzSChh-F2fyJDTKpg%40mail.gmail.com > <https://groups.google.com/d/msgid/django-users/CAMKMUjvhmpEbB4LeEBnYX5-e8LPVb3m7wpzSChh-F2fyJDTKpg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Django users" group. 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