Model Observer

Model Observer is a Django package that provides functionality to track events of the model. Based on django signals.

ModelObserver class will observe model behavior and triggers different signals.

Installation

Use the package manager pip to install model_observer.

pip install model_observer

Available signals

class ModelObserver:
    _available_signal_types = ('pre_init', 'post_init', 'pre_save', 'post_save',
                               'pre_delete', 'post_delete', 'm2m_changed',
                               'pre_migrate', 'post_migrate')

Usage

from model_observer.model import ModelObserver

class Blog(Model, ModelObserver):
    title = models.CharField(max_length=50)

    def on_delete(self, **kwargs):
        print('Object was deleted!')
        print('self', self.__dict__)
        print('kwargs', kwargs)

    def on_create(self, **kwargs):
        print('Object was created!')
        print('self', self.__dict__)
        print('kwargs', kwargs)

    def on_update(self, **kwargs):
        print('Object was updated!')
        print('self', self.__dict__)
        print('kwargs', kwargs)

Create object

from blogs.models import Blog
blog = Blog.objects.create(title='test1')

Output

Object was created!
self {'_state': <django.db.models.base.ModelState object at 0x0000013FDE855640>, 'id': 2, 'title': 'test1'}
kwargs {'signal': <django.db.models.signals.ModelSignal object at 0x0000013FDD6A93A0>, 'sender': <class 'blogs.models.Blog'>, 'instance': <Blog: Blog object (2)>, 'created': True, 'update_fields': None, 'raw': False, 'using': 'default'}

Update object

from blogs.models import Blog
blog = Blog.objects.get(pk=1)
blog.title = 'test 1!'
blog.save()

Output

Object was updated!
self {'_state': <django.db.models.base.ModelState object at 0x0000024B609A8FA0>, 'id': 1, 'title': 'test 1!', '_pre_save_instance': <Blog: Blog object (1)>, '_pre_delete_instance': <Blog: Blog object (1)>}
kwargs {'signal': <django.db.models.signals.ModelSignal object at 0x0000024B5F69FCD0>, 'sender': <class 'blogs.models.Blog'>, 'instance': <Blog: Blog object (1)>, 'created': False, 'update_fields': None, 'raw': False, 'using': 'default'}

Delete object

from blogs.models import Blog
blog = Blog.objects.get(pk=3)
blog.delete()

Output

Object was deleted!
self {'_state': <django.db.models.base.ModelState object at 0x00000182BA476AC0>, 'id': 3, 'title': 'test1'}
kwargs {'signal': <django.db.models.signals.ModelSignal object at 0x00000182B92985E0>, 'sender': <class 'blogs.models.Blog'>, 'instance': <Blog: Blog object (3)>, 'using': 'default'}
(1, {'blogs.Blog': 1})

Observe the object field

Integration

class Blog(models.Model, ModelObserver):
    ...

    def title_changed(self, **kwargs):
        print('Field `title` was changed!')
        print('self', self.__dict__)
        print('kwargs', kwargs)
        
        instance = kwargs.get('instance')  # Work with instance
        ...

from blogs.models import Blog
blog = Blog.objects.first()
blog.title = 'Test 2!'
blog.save()

Output

Field `title` was changed!
self {'_state': <django.db.models.base.ModelState object at 0x0000023ED4BF4700>, 'id': 4, 'title': 'Test 2!', '_pre_save_instance': <Blog: Blog object (4)>, '_pre_delete_instance': <Blog: Blog object (4)>}
kwargs {'signal': <django.db.models.signals.ModelSignal object at 0x0000023ED3A48280>, 'sender': <class 'blogs.models.Blog'>, 'instance': <Blog: Blog object (4)>, 'raw': False, 'using': 'default', 'update_fields': None}

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT