A django model mixin that makes it easy to react to field value changes on models. Supports an API similar to the model clean method.
Given that I have the model
class MyModel(models.Model):
mai_field = models.CharField()
other_field = models.BooleanField()
And I want to be notified when mai_field's value is changed and
persisted I would simply need to modify my model to include a
ondelta_mai_field method.
from ondelta.models import OnDeltaMixin
class MyModel(OnDeltaMixin):
mai_field = models.CharField()
other_field = models.BooleanField()
def ondelta_mai_field(self, old_value, new_value):
print("mai field had the value of {}".format(old_value))
print("but after we called save it had the value of {}".format(new_value))
This is the easiest method to watch a single field for changes, but
what if we want to perform an action that has an aggregate view
of all of the fields that were changed? OnDeltaMixin provides an
ondelta_all method for these cases; it is only called once for
each save.
from ondelta.models import OnDeltaMixin
class MyModel(OnDeltaMixin):
mai_field = models.CharField()
other_field = models.BooleanField()
ondelta_all(self, fields_changed):
if 'mai_field' in fields_changed and 'other_field' in fields_changed:
print("Both fields changed during this save!")
Some field types are not supported: ManyToManyField, reverse ManyToManyField,
reverse ForeignKey, and reverse OneToOneField relations. If you create an
ondelta_field_name method for one of these fields, it will not be called when
that field is changed.
I like to help people as much as possible who are using my libraries, the easiest way to get my attention is to tweet @adamhaney or open an issue. As long as I'm able I'll help with any issues you have.