Django中2个型号的关系

Question

I have two models- Order and Expense. The expense is a crud list respective to the particular Order. How can I make such a relationship between these two models?

models.py - Order

class Order(models.Model):

    user = models.ForeignKey(User,on_delete=models.CASCADE,related_name="order",blank=True,null=True)
    client_name = models.CharField(max_length=100)
    event_name = models.CharField(max_length=100)
    contact = models.CharField(max_length=15)
    event_date = models.DateField(auto_now_add=False,auto_now=False)
    expenses = models.IntegerField(default=0,null=True,blank=True)

Models.py - Expense

class ProjectExpense(models.Model):
    user = models.ForeignKey(User,on_delete=models.CASCADE,related_name="project_expense",null=True,blank=True)
    order_id = models.IntegerField(default='0')
    exp = models.CharField(max_length=100)
    exp_desc = models.TextField(null=True,blank=True)
    amount = models.IntegerField(default='0')

    def __str__(self):
        return self.exp

I tried assigning the field Order ID with the current Order. But how will I able to pass the current Order.

Answer 1

I'm guessing you need a ManyToOne Relationship: One Order can have multiple expenses?

For that you can remove the expenses property from the Order model. And you need to modify the order_id property of the ProjectExpense model like this (as @Lambo already commented):

order = models.ForeignKey(Order, on_delete=models.CASCADE)

When you are querying the Order model the related Expenses will be included if you ask for them and vice versa.

The Objects are created as following in the backend:

new Order:

# input contains the data received from frontend
Order.objects.create(user_id=input.user_id,
                     client_name=input.client_name,
                     event_name=input.event_name,
                     contact=input.contact,
                     event_date=input.event_date)

new Expense:

# input contains expense details received from frontend
ProjectExpense.objects.create(user_id=input.user_id,
                              order_id=input.order_id,
                              exp=input.exp,
                              exp_desc=input.exp_desc,
                              amount=input.amount)

It is important that you write order_id= although the property in the model itself is called order .

Answer 2

Thanks all for providing me the answers. The feature I'm looking at is GenericForeignKey. This tutorial helped me understand it.

The working of Expenses associated with the respective Order, is way similar to the Comments and Post like in blogs.