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djangodjango-modelsreference

How to save a field from another model to a variable NOT A FIELD

I have a model called Actual:

# Actual parts table
class Actual(models.Model):
    vendor = models.ForeignKey(Vendor, on_delete=models.CASCADE, verbose_name="Vendor name", related_name="actualvendor")       
    number = models.CharField("External part number", max_length=32, unique=True, blank=True, null=True)     
    description = models.CharField(max_length=64, blank=True)                                     
    pq = models.DecimalField(max_digits=7, decimal_places=2, default=1)                                                           
    mrrp = models.DecimalField(max_digits=10, decimal_places=2)     
    # Model metadata
    class Meta:
        unique_together = ["vendor", "number"]
        verbose_name_plural = "actual external parts"
    # Display below in admin 
    def __str__(self): 
       return f"{self.number}"

I also have another model called Offer:

class Offer(models.Model):
    sync_id = models.ForeignKey(Sync, on_delete=models.CASCADE, verbose_name="Internal part number", related_name="part")
    discount = models.DecimalField(max_digits=3, decimal_places=2, default=0)   
    moq = models.DecimalField(max_digits=4, decimal_places=2, default=1)                                              
    status = models.CharField(max_length=20, choices=OFFERSTATUS_CHOICES, default=1)
    actual = models.OneToOneField(Actual, on_delete=models.CASCADE)
    # Display something in admin
    def __str__(self):
        return f"Offer {self.id} for {self.sync_id}"

    # Calculate the price
    def price(self):
        return self.actual.mrrp * (1-self.discount)

I am trying to calculate the 'price' in the 'Offer' model using 'mrrp' but 'mrrp' is from the 'Actual' model.

I am able to do so with the code I've attached but as you can see in the django admin, the 'actual' shows up as a field. I don't want it to appear as a field. I just want 'actual' to be a variable that is equal to the value of 'mrrp'. That way I can use it to calculate the price. Django admin view of adding an Offer

Is there another way to reference fields from another model? Surely fields aren't the only way?

Solution

  • I solved this with a property decorator. I had the right idea but did not place a property decorator on top of the function that calculates the price. Use a property decorator to display the data as you would a field in Django.

    I added the below to the bottom of my model:

        @property
    def price(self):
        return self.actual.mrrp * (1-self.discount)