Скачать или смотреть How to Get the Object When Validated in Your Django Form's Clean Function?

Learn how to properly access object instances in Django forms using the clean method. We'll help you solve common issues with slug-based data retrieval and validation errors.
---
This video is based on the question https://stackoverflow.com/q/63957460/ asked by the user 'Salivanch' ( https://stackoverflow.com/u/14111912/ ) and on the answer https://stackoverflow.com/a/63960491/ provided by the user 'Andrey Maslov' ( https://stackoverflow.com/u/7186864/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How can I get the object when validated, in the clean function?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Introduction

When working with Django forms, particularly when using the ModelForm, you might encounter a common scenario where you need to validate input against existing records. A frequent question is: How can I get an object when validated in the clean function? This post will walk you through the process of correctly accessing an object in your clean() method of a Django form.

In this case, we'll explore how to retrieve an Item object by its slug field and check whether the number of items sold does not exceed the number of items on hand. This validation is crucial for maintaining accurate inventory records and preventing sales errors.

The Problem

The original code provided results in an error, indicating that the NewDateSell object does not have access to kwargs, which is necessary for obtaining the appropriate slug. Here’s a brief look at the relevant part of the error message:

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

Solution Overview

To resolve this issue, we’ll need to adjust how our form class NewDateSell is constructed and how it retrieves the slug parameter. Additionally, we’ll modify the clean() method to ensure it operates as intended. Below are the steps we can take to achieve this.

1. Modify the Form Class

We need to add the slug as a parameter in the NewDateSell form class. Also, the clean method should return a dictionary rather than a single value. Here’s the modified form class:

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

Key Changes Made:

Slug Handling: We store the slug from kwargs into the class attribute during initialization.

Returning a Dict: The clean() method now returns cleaned_data, which is a dictionary containing all necessary validated data.

2. Adjust the View Class

In the SellPage view class, we need to ensure we pass the slug to the form correctly. We can accomplish this through the get_form_kwargs method. Here’s how you might do it:

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

Key Adjustments:

Passing Slug: We append the slug to kwargs that are passed to the form.

Conclusion

By implementing these changes, you should eliminate the error regarding the absence of kwargs and successfully manage the validation of items against their sold quantities. Understanding how to manipulate the clean method and pass parameters in Django forms is essential for robust application development.

Feel free to reach out if you have any further questions or if you’d like to dive deeper into the Django framework! Happy coding!