Django: Constraint on multiple model fields

Question

Example:

class Author(models.Model):
    first_name = models.CharField()
    last_name = models.CharField()

    def _get_full_name(self):
       return '{0} {1}'.format(self.first_name, self.last_name)

   full_name = property(_get_full_name)

What's the recommended way of putting a unique constaint on the full_name? Was thinking of overwriting save but maybe there are better solutions?

similar: http://stackoverflow.com/questions/2201598/django-how-to-define-two-fields-unique-as-couple — manji, May 13 '11 at 15:08

score 4 · Accepted Answer · answered May 13 '11 at 15:10

4

Take a look at the Meta class option unique_together

You could do it this way:

class Author(models.Model):
    first_name = models.CharField()
    last_name = models.CharField()

    def _get_full_name(self):
       return '{0} {1}'.format(self.first_name, self.last_name)

    full_name = property(_get_full_name)

    class Meta: 
       unique_together = ("first_name", "last_name")

The advantage is that this is enforced at the DB level with the proper UNIQUE SQL statements.

answered May 13 '11 at 15:10

Lou Franco

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It is probably the solution required, but there are edge cases that this won't pick up as a conflict: "'bob' 'brown smith'" and "'bob brown' 'smith'". Full name is the same, but last_name and first_name are different. – Matthew Schinckel May 15 '11 at 09:59

score 2 · Answer 2 · answered May 13 '11 at 15:07

2

unique_together

unique_together = ("first_name", "last_name")

answered May 13 '11 at 15:07

JamesO

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Django: Constraint on multiple model fields

2 Answers2