Скачать или смотреть How to Add a Custom OrderingFilter with Nulls Last in Django

Discover how to customize the `OrderingFilter` in Django to handle null values efficiently with our step-by-step guide. Ideal for developers working with Django Rest Framework!
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This video is based on the question https://stackoverflow.com/q/64640595/ asked by the user 'Ali Soltani' ( https://stackoverflow.com/u/6173668/ ) and on the answer https://stackoverflow.com/a/64641189/ provided by the user 'Ali Soltani' ( https://stackoverflow.com/u/6173668/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Customizing Ordering Filters in Django

When working with Django, especially with the Django Rest Framework, you often need to implement advanced filtering options for your queryset. One common scenario is adding an ordering filter that handles null values effectively. Specifically, you may want to order your data by a field—such as created—while ensuring that null values appear at the end of the list. This guide will explore how to achieve this using a custom OrderingFilter.

The Problem

You want to add an ordering filter based on a specific field, such as created, and ensure that any null values are handled gracefully. You might find yourself with a query structure like this:

[[See Video to Reveal this Text or Code Snippet]]

In your Django application, you might already have a filter set up like this:

[[See Video to Reveal this Text or Code Snippet]]

However, this default setup does not account for the null values in the ordering process. So, let's dive into the solution!

Solution: Create a Custom Ordering Filter

To address this, we'll create a custom OrderingFilter that incorporates the desired logic for handling null values. Here’s how you can implement it:

Step 1: Define the Custom Filter

Start by defining a new class that extends filters.OrderingFilter. We will override the filter method to incorporate the logic for sorting null values:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Code

Check for Empty Values: If the ordering value is empty, return the original queryset (qs).

Map Values to Ordering: Convert the incoming values into a format that Django can understand by checking the sign (- for descending and default for ascending).

Order by Null Last: Use F() objects to specify the ordering while using desc(nulls_last=True) and asc(nulls_last=True) appropriately.

Step 2: Integrate Custom Filter with Your Filter Set

Now, update your ProductFilter to use the newly created NullsLastOrderingFilter:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the steps outlined in this post, you can effectively manage ordering in your Django application while ensuring that null values are placed last in the sorted output. This solution enhances user experience by providing clear and organized results in your API responses.

Implementing a custom OrderingFilter might seem complex at first, but it provides significant benefits, especially when dealing with real-world data scenarios where null values are common. Happy coding!