CODEWITHSUNDEEP
django
paolo
paolo

Reputation: 359

ForeignKey or ManyToMany - When to use? Which version is better?

ForeignKey or ManyToMany - When to use? I wonder which version is better. InvoiceHistory model will be stored status changes of Invoice

REJECTED = 1
SUBMITTED = 2
APPROVED = 3
HISTORY_CHOICES = (
    REJECTED, "Rejected",
    SUBMITTED, "Submitted",
    APPROVED, "Approved",
)

class InvoiceHistory(TimeStampedModel)
    user = models.ForeignKey(settings.AUTH_USER_MODEL)
    action = models.IntegerField(choices=HISTORY_CHOICES)

class Invoice(models.Model):
    number = models.CharField(...)
    history = models.ManyToManyField(InvoiceHistory)

or version with ForeignKey:

class Invoice(models.Model):
    number = models.CharField(...)

class InvoiceHistory(TimeStampedModel)
    user = models.ForeignKey(settings.AUTH_USER_MODEL)
    action = models.IntegerField(choices=HISTORY_CHOICES)
    invoice = models.ForeignKey(Invoice)

Upvotes: 1

Views: 63

Answers (1)

bruno desthuilliers
bruno desthuilliers

Reputation: 77902

It's not a question of "which is better", but of "which one correctly models your domain". In your first example, you have a many to many relationship between Invoice and InvoiceHistory, which means that a same InvoiceHistory instance can belong to many Invoice instances. I don't have your project's full context but I'm not sure it makes sense here...

Upvotes: 1

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