How Can I Migrate Models Between Django Apps Using Django 1.7?

Migrating Models Between Django Apps Using Django 1.7

As a developer, encountering disorganization in your project's structure can be a common concern. In the context of Django models, managing them effectively across different applications is crucial. Prior to Django 1.7, this process was challenging, particularly with foreign key considerations.

However, Django 1.7 introduces a significant improvement with built-in support for database migrations. This enables a more efficient approach to the task of moving models between apps.

The Process

1. Remove Model from Old App:

• Create an empty migration for the old app.
• Define a SeparateDatabaseAndState operation in the migration to concurrently rename the model table.
• Delete the model from the old app's history using a state operation.

Example:

<code class="python"># makemigrations old_app --empty
class Migration(migrations.Migration):
    dependencies = []
    database_operations = [
        migrations.AlterModelTable('TheModel', 'newapp_themodel')
    ]
    state_operations = [
        migrations.DeleteModel('TheModel')
    ]
    operations = [
        migrations.SeparateDatabaseAndState(...)
    ]</code>

2. Add Model to New App:

• Copy the model to the new app's model.py file.
• Creating a migration for the new app will generate a CreateModel operation.
• Wrap this operation in a SeparateDatabaseAndState operation to prevent recreating the table.
• Specify the previous migration as a dependency.

Example:

<code class="python"># makemigrations new_app
class Migration(migrations.Migration):
    dependencies = [('old_app', 'above_migration')]
    state_operations = [
        migrations.CreateModel(...)
    ]
    operations = [
        migrations.SeparateDatabaseAndState(...)
    ]</code>

By following these steps, you can successfully move models between Django apps, maintaining database integrity and simplifying your project structure.

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