How create new object automatically after creating other object in django?

Question

For example, I have two classes.

class Book(models.Model):
    title = models.CharField (...)    
    author = models.CharField (...)
    price = models.Integer(...)

class Order(models.Model)
    order_datetime = models.DateTimeField()
    order_book = models.ForeignKey(Book,....)

New Order object should be created automatically after each addition of a new Book object in the database. And order_book fielt should be autocomplited with correspending book object.

How can I make it?

Thanx for the help!

Possible duplicate of Can Django automatically create a related one-to-one model? — Ciro Santilli OurBigBook.com
– Ciro Santilli OurBigBook.com, Commented May 10, 2016 at 21:32

nima · Accepted Answer · 2015-02-01 16:15:44Z

3

You can override the save method of Book:

class Book(models.Model):
    title = models.CharField (...)    
    author = models.CharField (...)
    price = models.Integer(...)

    def save(self, *args, **kwargs):
        is_new = True if not self.id else False
        super(Book, self).save(*args, **kwargs)
        if is_new:
            order = Order(order_book=self)
            order.save()

You can also add auto_now_add=True to order_datetime if it's supposed to be filled with insertion time:

order_datetime = models.DateTimeField(auto_now_add=True)

answered Feb 1, 2015 at 16:15

nima

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4 Comments

igorshi1 Over a year ago

Thanx a lot, nima! I will try to use it.

Asaduzzaman Sohel Over a year ago

this line I can't understand ``` is_new = True if not self.id else False

nima Over a year ago

You need to to decide whether the Book is saved for the first time, before calling super because it will have an id after that anyways.

fluffykitten Over a year ago

when I try to do this I get an error in order_book, Im guessing its because when creating an order the book is not a parameter

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