Common recipes
==============


.. note:: Most recipes below take on Django model examples, but can also be used on their own.


Dependent objects (ForeignKey)
------------------------------

When one attribute is actually a complex field
(e.g a :class:`~django.db.models.ForeignKey` to another :class:`~django.db.models.Model`),
use the :class:`~factory.SubFactory` declaration:


.. code-block:: python

    # models.py
    class User(models.Model):
        first_name = models.CharField()
        group = models.ForeignKey(Group)


    # factories.py
    import factory
    from . import models

    class UserFactory(factory.Factory):
        FACTORY_FOR = models.User

        first_name = factory.Sequence(lambda n: "Agent %03d" % n)
        group = factory.SubFactory(GroupFactory)


Reverse dependencies (reverse ForeignKey)
-----------------------------------------

When a related object should be created upon object creation
(e.g a reverse :class:`~django.db.models.ForeignKey` from another :class:`~django.db.models.Model`),
use a :class:`~factory.RelatedFactory` declaration:


.. code-block:: python

    # models.py
    class User(models.Model):
        pass

    class UserLog(models.Model):
        user = models.ForeignKey(User)
        action = models.CharField()


    # factories.py
    class UserFactory(factory.Factory):
        FACTORY_FOR = models.User

        log = factory.RelatedFactory(UserLogFactory, 'user', action=models.UserLog.ACTION_CREATE)


When a :class:`UserFactory` is instantiated, factory_boy will call
``UserLogFactory(user=that_user, action=...)`` just before returning the created ``User``.