[FIXED] Django Save method giving an error trying to add a new record to table

Issue

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.

Solution

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.

Answered By - NixonSparrow