CODEWITHSUNDEEP
pythondjango
user3361761
user3361761

Reputation: 259

Trying to query for all objects with a foreign key reference to an entry with a certain value in one of its fields

The title might look a little confusing. However, what I am trying to do is quite simple. I have the following models:

class ListEntry(models.Model):
    name = models.CharField(max_length=64)
    expire_date = models.DateField('date of expiration')
    create_date = models.DateField('date created')

class ListWarning(models.Model):
    mailing_list = models.ForeignKey(ListEntry)
    first_warning = models.BooleanField()
    last_warning = models.BooleanField()

I want to query for a List Warning object that references a mailing list with a certain name. Here's an example:

first_warning_list = ListWarning.objects.filter(mailing_list.name='PH_212', first_warning=True, last_warning=False)

However, for some reason, python is complaining of a syntax error:

first_warning_list = ListWarning.objects.filter(mailing_list.name='PH_212', first_warning=True, last_warning=False)
SyntaxError: keyword can't be an expression

What is the syntactically correct way to do this query?

Upvotes: 0

Views: 19

Answers (1)

Alex
Alex

Reputation: 8539

Use double underscores rather than dot notation to refer to mailing_list name 

first_warning_list = ListWarning.objects.filter(mailing_list__name='PH_212', first_warning=True, last_warning=False)

Docs here.

Django offers a powerful and intuitive way to “follow” relationships in lookups, taking care of the SQL JOINs for you automatically, behind the scenes. To span a relationship, just use the field name of related fields across models, separated by double underscores, until you get to the field you want.

Upvotes: 2

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