django post_save: update_or_create 不工作

Question

class SubjectSectionTeacher(models.Model):
    Education_Levels = models.ForeignKey(EducationLevel, related_name='+', on_delete=models.CASCADE, blank=True)
    Courses = models.ForeignKey(Course, related_name='+', on_delete=models.CASCADE, null=True, blank=True)
    Sections = models.ForeignKey(Section, related_name='+', on_delete=models.CASCADE, null=True)




class StudentsEnrollmentRecord(models.Model):
    Student_Users = models.ForeignKey(StudentProfile, related_name='students', on_delete=models.CASCADE, null=True)
   Courses = models.ForeignKey(Course, related_name='+', on_delete=models.CASCADE, null=True, blank=True)
    Section = models.ForeignKey(Section, related_name='+', on_delete=models.CASCADE, null=True, blank=True)
    Education_Levels = models.ForeignKey(EducationLevel, related_name='+', on_delete=models.CASCADE, blank=True,



class StudentsEnrolledSubject(models.Model):
        Students_Enrollment_Records = models.ForeignKey(StudentsEnrollmentRecord, related_name='+',
                                                        on_delete=models.CASCADE, null=True)
        Subject_Section_Teacher = models.ForeignKey(SubjectSectionTeacher, related_name='+', on_delete=models.CASCADE,
                                                    null=True,blank=True)      

    @receiver(post_save, sender=StudentsEnrollmentRecord)
            def create(sender, instance, created, *args, **kwargs):
                teachers = SubjectSectionTeacher.objects.filter(Sections=instance.Section,
                                                                Education_Levels=instance.Education_Levels,
                                                                Courses=instance.Courses)
            for each in teachers:
                if created or teachers.exists():
                    print("if")
                    StudentsEnrolledSubject.objects.create(
                        pk=each.id,
                        Students_Enrollment_Records=instance,
                        Subject_Section_Teacher=each

                    )

插入数据工作正常，但是当我更新现有数据时，它会创建另一条记录而不是更新

注意：我已经尝试过 StudentsEnrolledSubject.objects.create 和 StudentsEnrolledSubject.objects.update_or_create，但结果仍然相同

Answer 1

问题出在您的 if 语句和您创建新实例的方式上。尝试更改代码如下：

 for each in teachers:
     StudentsEnrolledSubject.objects.create_or_update(
            Students_Enrollment_Records=instance,
            Subject_Section_Teacher=each
     )

Answer 2

条件

for each in teachers:
    if created or teachers.exists():

是错误的，teachers.exists() 将 始终为真，因为您已经遍历了 teachers.

另一个问题是，signal functions shouldn't be an instance/class method - 将它移出模型。目前 sender 参数实际上是 self 等等，所以 created 也是错误的。（或者给它一个 @staticmethod 装饰器）

由于您只想在 StudentsEnrollmentRecord 创建期间创建记录，因此您应该在信号函数的开头处理 created 参数 - 这也为您节省了一些查询。

另外，给你的信号函数一个更有意义的名字，也许generate_subjects?

所以信号可能看起来像这样

@receiver(post_save, sender=StudentsEnrollmentRecord)
def create(sender, instance, created, *args, **kwargs):
    if not created:
        return
    teachers = SubjectSectionTeacher.objects.filter(...)
    for each in teachers:
        StudentsEnrolledSubject.objects.create(...)


class StudentsEnrolledSubject(models.Model):
   ...

django post_save: update_or_create 不工作

django post_save: update_or_create not working

python

django

django-signals