外键字段Django上的实例错误

Question

我很困惑，在我的功能上需要帮助。我有两张桌子学生和学生的信息。学生信息是那个学生的全部监护人信息。我将这些数据从主学生表中分离出来，这样您就可以将任意数量的监护人添加到有新记录的学生文件中。我得到的错误如下所示。

无法分配“1”："StudentInformation.studentpsid“必须是”学生“实例。

附件你会看到我的密码。学生信息是学生的外键。

def ImportStudentGuardian(request):
    AuthTokenP(request)
    print("Getting student guardian data from SIS for K-8")
    #Pulls K-8 Guardians
    url = "removed for posting"
    payload = {}
    token = APIInformation.objects.get(api_name="PowerSchool")
    key = token.key
    headers = {'Authorization': 'Bearer {}'.format(key)}   
    response = requests.request("GET", url, headers=headers, data = payload)
    encode_xml = response.text.encode('utf8')
    xml_string = ET.fromstring(encode_xml)
    students = xml_string.findall("student")
    for student in students:
      #XML Values
      psid = student.find("id").text
      try:
       mother = student.find("contact").find("mother").text
      except Exception:
       mother = ""   
      try: 
       father = student.find("contact").find("father").text
      except Exception:
       father = "" 
      if Student.objects.filter(studentpsid=psid).exists():  
        print("Accessing guardian information.")
        m = StudentInformation.objects.create(studentpsid=psid,guardian_name = mother, relation = "Mom")   <---- Function Fails here
        print("Record doesn't exist for mom, creating record.")
        m.save()
        d= StudentInformation.objects.create(studentpsid=psid,guardian_name = father, relation = "Dad")
        print("Record doesn't exist for dad, creating record.")
        d.save()
      return ("Updated Guardian Information ")

Model

class Student(models.Model):
    studentpsid= models.CharField(primary_key = True , default = "", max_length = 50, unique = True)
    student_name = models.CharField(max_length = 50)
    first_name = models.CharField(max_length = 50, default = "")
    last_name = models.CharField(max_length = 50,default = "")
    gender = models.CharField(max_length = 1,default = "")
    student_grade = models.CharField(max_length = 2, default = "")
    home_room = models.CharField(max_length = 5, default = "")
    student_enrollment = models.CharField(max_length = 2, default = "")
    school_number = models.CharField(max_length = 15, default = "") 
    email = models.EmailField(default = "")
    projected_graduation_year = models.CharField(max_length = 4, default = "")
    counseling_goal = models.TextField(max_length = 255)
    class_name = models.ManyToManyField(TeacherClass)
    image = models.ImageField(default ="default.png", upload_to ='student_pics')

# Guardian Information For Student 
class StudentInformation(models.Model):
      studentpsid = models.ForeignKey(Student,on_delete = models.CASCADE, default = "" ,) 
      guardian_name = models.CharField(max_length = 50, default = "")
      RELATION_CHOICES = [
        (0, 'None'),  
        (1, 'Mom'),
        (2, 'Dad'),
        (3, 'Other'),
             ]
      relation = models.PositiveSmallIntegerField(choices = RELATION_CHOICES,)
      guardian_cell = models.CharField(max_length = 12, default = "")
      guardian_email = models.EmailField(max_length = 80,blank = True, default = "")
      prefered_contact = models.BooleanField(default = False, blank = True)
      DAY_CHOICES = [
        (0, 'None'),  
        (1, 'Monday'),
        (2, 'Tuesday'),
        (3, 'Wednesday'),
        (4, 'Thursday'),
        (5, 'Friday'),
             ]
      day_of_week =  models.PositiveSmallIntegerField(choices = DAY_CHOICES, default = 0 )
      time = models.CharField(max_length= 7, default = "", blank = True)

Answer 1

在使用外键关系创建记录时，应该提供相关表的实例，以便表能够维护该特定记录的关系。

使用给定的Student获取psid表的实例，并在创建StudentInformation记录时使用该实例

编辑：仅在mother和father值可用时包含用于创建记录的部分。

for student in students:
      #XML Values
    psid = student.find("id").text
    try:
        psid_obj = Student.objects.get(studentpsid=psid) #(pk = psid) also works as the field is primary key
        try:
            mother = student.find("contact").find("mother").text
            m = StudentInformation.objects.create(studentpsid=psid_obj,guardian_name = mother, relation = "Mom")
            m.save()
        except Exception as err1:
            print "Error at Mom", str(err1)   
        try: 
            father = student.find("contact").find("father").text
            d= StudentInformation.objects.create(studentpsid=psid_obj,guardian_name = father, relation = "Dad")
            d.save()
        except Exception as err2:
            print "Error at Dad",str(err2)
    except:
        print "Student Record Not found"

Answer 2

正如错误所述，您正在将一个char数据类型分配给ForeignKey字段。

您应该首先获取该Student的实例，然后将其分配给您的StudentInformation对象，如下所示：

if Student.objects.filter(studentpsid=psid).exists():  
        print("Accessing guardian information.")
        student = Student.objects.get(pk=psid)  # this will fail if the student doesn't exist
        m = StudentInformation.objects.create(studentpsid=student,guardian_name = mother, relation = "Mom")   <---- Function Fails here
        print("Record doesn't exist for mom, creating record.")
        m.save()
        d= StudentInformation.objects.create(studentpsid=student,guardian_name = father, relation = "Dad")
        print("Record doesn't exist for dad, creating record.")
        d.save()
      return ("Updated Guardian Information ")