django-tracking-model 0.1.0

Track changes made to django model instance.

Django Tracking Model 🏁

Track changes made to your model's instance.
Changes are cleared on save.
This package is intented to be used mainly with signals.
Mutable fields (e.g. JSONField) are not handled with deepcopy to keep it fast and simple.
Meant to be model_utils's FieldTracker fast alternative.

Usage

from django.db import models
from tracking_model import TrackingModelMixin

# order matters
class Example(TrackingModelMixin, models.Model)
    text = models.TextField(null=True)
    self = models.ForeignKey("self", null=True)
    array= models.ArrayField(TextField())

In [1]: e = Example.objects.create(id=1, text="Sample Text")
In [2]: e.tracker.changed, e.tracker.newly_created
Out[1]: ({}, True)
In [3]: e.text = "Different Text"
In [4]: e.tracker.changed
Out[2]: {"text": "Sample Text"}
In [5]: e.save()
In [6]: e.tracker.changed, e.tracker.newly_created
Out[3]: ({}, False)

DTM will also detect changes made to ForeignKey/OneToOne fields

In [1]: Example.objects.create(self=e)
In [2]: e.self = None
In [3]: e.tracker.changed
Out[1]: {"self_id": 1}

Because DTM does not handle mutable fields well you handle them with copy/deepcopy

In [1]: e = Example.objects.create(array=['I', 'am', 'your'])
In [2]: copied = copy(e.array)
In [3]: copied.append('father')
In [4]: e.array = copied
In [5]: e.tracker.changed
Out[1]: {'array': ['I', 'am', 'your', 'father']}

DTM works best with *_save signals

def pre_save_example(instance, *args, **kwargs):
    # .create() does not populate .changed, we use newly_created
    if 'text' in instance.tracker.changed or instance.tracker.newly_created:
      if instance.text
          instance.array = instance.text.split()

pre_save.connect(pre_save_example, sender=Example)

In [1]: e = Example.objects.create(text='I am your father')
In [2]: e.refresh_from_db() # not needed
In [3]: e.array
Out[1]: ['I', 'am', 'your', 'father']

Requirements

• Python >= 2.7, <= 3.7
• Django >= 1.9, <= 2.2

Todo

• Tests could be more readable
• Signals decorators