Django Save method giving an error trying to add a new record to table-CodePudding

I have the following code in a view:

        lp_detail = LearningPathDetail()
        pos_in_path = 1
        lp_detail.lpheader_id = pk

        lesson_ids = request.POST["lesson_ids"].split(",")

        for lesson_id in lesson_ids:
            lp_detail.id = ""
            lp_detail.lesson_id = lesson_id
            lp_detail.pos_in_path = pos_in_path
            lp_detail.save()
            pos_in_path  = 1

pk is the ID from the header table that points back to the header record that identifies all of the detail records associated with it.

lesson_ids is a list of DB ids that need to be inserted into the lp_detail table.

What I think the code should do (according to the manual) based on the id being blank (I have also tried setting it to None) is create the record, but instead I get an error:

Field 'id' expected a number but got ''.

Here is the model for the LearningPathDetail table:

class LearningPathDetail(models.Model):
    lpheader = models.ForeignKey(LearningPathHeader, on_delete=models.CASCADE)
    lesson = models.ForeignKey(Lesson, on_delete=models.CASCADE, blank=True, null=True)
    pos_in_path = models.IntegerField(default=1)

I am not sure what I have incorrect here.

CodePudding user response：

Why would you want to set value of id to empty string? Just delete this row:

lp_detail.id = ""

And let Django find good id by itself.

Also, I thin you want this:

lp_detail = LearningPathDetail()

Inside the loop. You might need new object with every iteration.

CodePudding user response：

Pk / Primary Key / Row Number cannot be blank.

It should just be something like: (and Django will take care of all the PK stuff

# get header
headerObj = LearningPathHeader.objects.get(pk=pk)

lesson_ids = request.POST["lesson_ids"].split(",")

pos_in_path = 1
for i in lesson_ids:
    # Get lesson Object
    lessonObj = Lesson.objects.get(pk=i)

    # create detail Obj
    LearningPathDetail.objects.create(
        lpheader= headerObj,
        lesson= lessonObj,
        opos_in_path= pos_in_path.
    )
    pos_in_path  = 1

if LearningPathHeader is unique to the LearningPathDetail. (Example only 1 path can have the header 'science') Then you'd just want to remove all the previous paths

lesson_ids = request.POST["lesson_ids"].split(",")

headerObj = LearningPathHeader.objects.get(pk=pk)

# delete all the old Path!
LearningPathDetail.filter(lpheader=headerObj).delete()


pos_in_path = 1
for i in lesson_ids:
    lessonObj = Lesson.objects.get(pk=i)

    LearningPathDetail.objects.create(
        lpheader= headerObj,
        lesson= lessonObj,
        opos_in_path= pos_in_path.
    )
    pos_in_path  = 1