Question

我在使用Python 2.7.13（x86）的Django 1.6中有一个例外，我不知道要解决这个问题。我已经在其他帖子中搜索了答案，但无济于事。我被困在这上面，并且已经旋转了一段时间。

这是抛出异常的代码行：

myNewClass.class_students = selectedClass.class_students.all()

请参阅下面的完整代码示例...

这是我收到的错误消息：

Cannot set values on a ManyToManyField which specifies an intermediary model.  Use MyApp.ClassStudents's Manager instead.

（对于上述错误消息，我的应用程序被称为＆＃39; MyApp＆＃39; ...）

似乎所有（）都不起作用，无论如何要解决这个问题？你能帮助我解决这个问题，或者至少指出我正确的方向......

感谢。

这是我的代码：

class Class(models.Model):

    courseNumber = models.IntegerField()
    courseName = models.CharField(max_length = 32)

    class_students = models.ManyToManyField(Student, blank = True, through = 'ClassStudent')

class Student(models.Model):

    studentName = models.CharField(max_length = 32)
    overallStudentGPA = models.IntegerField()    

class ClassStudent(models.Model):

    myClass = models.ForeignKey(Class, on_delete = models.CASCADE)
    myStudent = models.ForeignKey(Student, on_delete = models.CASCADE)

    studentClassGrade = models.IntegerField()   

def copy_class(modeladmin, request, queryset):
    for selectedClass in queryset:

        myNewClass = Class(courseNumber = selectedClass.courseNumber, courseName = selectedClass.courseName)

        myNewClass.courseNumber = selectedClass.courseNumber
        myNewClass.courseName = selectedClass.courseName

        # Throws an error:
        # Cannot set values on a ManyToManyField which specifies an intermediary model.  Use MyApp.ClassStudents's Manager instead.
        myNewClass.class_students = selectedClass.class_students.all()

Answer 1

以下是我提出的答案：

def copy_class(modeladmin, request, queryset):

    myNewClass = Class(courseNumber = selectedClass.courseNumber, courseName = selectedClass.courseName)

    myNewClass.courseNumber = selectedClass.courseNumber
    myNewClass.courseName = selectedClass.courseName

    myNewClass.save()

    for studentObj in selectedClass.class_students.all():

        oneClassStudentObj = ClassStudents.get(class = selectedClass, student = studentObj)

        tempStudentClassGrade = oneClassStudentObj.studentClassGrade

        tempClassStudent = ClassStudent(myClass = myNewClass, myStudent = studentObj, studentClassGrade = tempStudentClassGrade )

        tempClassStudent.save()

我只是想知道是否有办法直接获取ClassStudent对象而不必使用ClassStudents.get（...）？它虽然有效......

Django 1.6，all（）抛出错误：无法在指定中间模型的ManyToManyField上设置值

1 个答案: