Django Lifecycle Hooks¶
This project provides a
@hook decorator as well as a base model and mixin to add lifecycle hooks to your Django models. Django's built-in approach to offering lifecycle hooks is Signals. However, my team often finds that Signals introduce unnecessary indirection and are at odds with Django's "fat models" approach.
In short, you can write model code like this:
from django_lifecycle import LifecycleModel, hook, BEFORE_UPDATE, AFTER_UPDATE class Article(LifecycleModel): contents = models.TextField() updated_at = models.DateTimeField(null=True) status = models.ChoiceField(choices=['draft', 'published']) editor = models.ForeignKey(AuthUser) @hook(BEFORE_UPDATE, when='contents', has_changed=True) def on_content_change(self): self.updated_at = timezone.now() @hook(AFTER_UPDATE, when="status", was="draft", is_now="published") def on_publish(self): send_email(self.editor.email, "An article has published!")
Instead of overriding
__init__ in a clunky way that hurts readability:
# same class and field declarations as above ... def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self._orig_contents = self.contents self._orig_status = self.status def save(self, *args, **kwargs): if self.pk is not None and self.contents != self._orig_contents): self.updated_at = timezone.now() super().save(*args, **kwargs) if self.status != self._orig_status: send_email(self.editor.email, "An article has published!")
- Python (3.5+)
- Django (2.0+)
pip install django-lifecycle
Either extend the provided abstract base model class:
from django_lifecycle import LifecycleModel, hook class YourModel(LifecycleModel): name = models.CharField(max_length=50)
Or add the mixin to your Django model definition:
from django.db import models from django_lifecycle import LifecycleModelMixin, hook class YourModel(LifecycleModelMixin, models.Model): name = models.CharField(max_length=50)
Read on to see more examples of how to use lifecycle hooks.