django_state_choice_field

It includes a StateChoiceField that comes with reusable TextChoices and validation for state changes. This feature enhances flexibility and data integrity.

Requirements

• Python 3.6+
• Django 2.2+

Installation

To set up django_state_choice_field, you can easily install it with pip.

$ pip install django_state_choice_field

Example

Consider a scenario where we have a model called Order that includes the storage of the order's payment status. This payment status can fall into one of the following in PaymentStatus.

It also defines the state transitions that are allowed for each state. For example, a payment status of IN_PROGRESS can only be changed to FAILED or COMPLETED. This is done by defining the __states__ attribute in the PaymentStatus class which extends StateEnum.

from django_state_choice_field import StateChoiceField, StateEnum

class PaymentStatus(StateEnum):
    NOT_STARTED = "not_started", "Not Started"
    IN_PROGRESS = "in_progress", "In Progress"
    COMPLETED = "completed", "Completed"
    FAILED = "failed", "Failed"
    CANCELLED = "cancelled", "Cancelled"
    NOT_REQUIRED = "not_required", "Not Required"

    __states__ = {
        NOT_STARTED: (),
        IN_PROGRESS: (NOT_STARTED, FAILED),
        FAILED: (IN_PROGRESS,),
        COMPLETED: (IN_PROGRESS, NOT_REQUIRED),
        NOT_REQUIRED: (IN_PROGRESS,),
        CANCELLED: (NOT_STARTED, NOT_REQUIRED, FAILED, COMPLETED),
    }

Model Order can be defined as follows. The payment_status field is defined as a StateChoiceField with the PaymentStatus enum class.

from django.db import models

class Orders(models.Model):
    product_name = models.CharField(max_length=100)
    payment_status = StateChoiceField(
        PaymentStatus, default=PaymentStatus.NOT_STARTED, max_length=20
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

Usage

>>> order = Order.objects.create(product_name="Product 1")
>>> order.payment_status
<PaymentStatus.NOT_STARTED: 'not_started'>

>>> order.payment_status = PaymentStatus.IN_PROGRESS
>>> order.save()

>>> order.payment_status
<PaymentStatus.IN_PROGRESS: 'in_progress'>

# Now, if we try to change the payment status to CANCELLED, it will raise a InvalidTransitionError error.
>>> order.payment_status = PaymentStatus.CANCELLED

django_state_choice_field.exceptions.InvalidTransitionError: [in_progress -> cancelled is not a valid transition for PaymentStatus']