Autofill database column after form submission in django

Question

Using Django 2.0 I have a model class named Book that asks for title, author, year but I have another column in that row that requires for a unique id based on the authors name, book title, and random numbers. This is my model

class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.CharField(max_length=50)
    year = models.PositiveSmallIntegerField()
    identification = models.CharField(max_length=50, blank=True)
    holder = models.ForeignKey('Person', related_name='book_holder', on_delete=models.PROTECT(), null=True, blank=True)
    available = models.BooleanField(default=True, blank=True)
    overdue = models.BooleanField(default=False, blank=True)

and it will be used in a form that only asks for the title, author, and year but what im looking for is how can i fill the identification column after the user submits the form. So for example if the user enters Harry Potter for the title and J. K. Rowling for the author, I want identification to have a value of a combination of both plus an eight digit random number at the end something like JH28194637 but I also need this column to be unique for every book so if i had to of the same Harry Potter books, I would need both to be different so one could be JH28194637 while the other one could be JH39287104. I will be using ajax to submit my form and I was thinking of maybe having a variable in my javascript that builds my identification when the user fills in the author and title fields and then passing it to my ajax call. Would that be the best way? But then how would I be able to check if the variable value already exists in the database or what would be the best way to do this task.

https://stackoverflow.com/questions/4269605/django-override-save-for-model#4269828 — dahrens, Jan 03 '18 at 22:33

score 1 · Answer 1 · answered Jan 03 '18 at 22:50

Since the two other fields are subject to change, and I assume that your identification field will also need to change, in terms of a unique integer you can always use that books model ID to make things simpler (unless you need to specify a particular id for certain books).

class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.CharField(max_length=50)
    year = models.PositiveSmallIntegerField()
    holder = models.ForeignKey('Person', related_name='book_holder', on_delete=models.PROTECT(), null=True, blank=True)
    available = models.BooleanField(default=True, blank=True)
    overdue = models.BooleanField(default=False, blank=True)
    @property
    def identification():
        a = self.author[:1].upper()
        t = self.title[:1].upper()
        id = str(self.id.zfill(10))
        return a+t+id

Autofill database column after form submission in django

1 Answers1