Solving the Rails Double Nested Form Issue with Active Admin

Discover how to efficiently implement double nested forms in your `Rails` application using `Active Admin` for effective management of variant colors and sizes. --- This video is based on the question https://stackoverflow.com/q/70026026/ asked by the user 'Hemant Patil' ( https://stackoverflow.com/u/4287118/ ) and on the answer https://stackoverflow.com/a/70028059/ provided by the user 'Allison' ( https://stackoverflow.com/u/4024628/ ) 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: Rails double nested form with active admin 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. --- Mastering Double Nested Forms with Active Admin in Rails Creating a complex data structure in your Ruby on Rails application can sometimes lead to issues, especially when you are working with nested forms. One common problem that developers face is how to handle double nested forms, particularly when using Active Admin to manage backend activities. This guide will explore a specific scenario involving variants, variant colors, and variant sizes, and provide a solution to ensure your forms are correctly rendered. The Problem: Double Nested Form Not Rendering Properly You have a Variant model that has many associated VariantColor objects, and each VariantColor has many VariantSize objects. While setting up your Active Admin forms, you’re encountering a situation where the variant_sizes form fields are not being populated under variant_colors. Below is the association structure of your models: Variant Has many VariantColor Accepts nested attributes for VariantColor VariantColor Belongs to Variant Has many VariantSize Accepts nested attributes for VariantSize Your current form setup looks like this: [[See Video to Reveal this Text or Code Snippet]] While the form for variant_colors is generating correctly, the form for variant_sizes does not appear as intended. Let’s break down how to approach this problem. Solution: Adjusting the Form and Permitted Parameters Step 1: Simplifying the Form Structure One quick test to resolve the rendering issue is to remove unnecessary wrappers around your f.has_many calls. Specifically, you can try removing the f.inputs and color_form.inputs that are enclosing the has_many blocks: Start by removing the first nested f.inputs around f.has_many :variant_colors. Similarly, you can remove color_form.inputs around color_form.has_many :variant_sizes. Here’s a simplified version of your form: [[See Video to Reveal this Text or Code Snippet]] Step 2: Permitting Parameters in Controller The next step is to ensure that your params are adequately permitted in the corresponding controller. The necessary parameters need to include attributes for both variant_colors and variant_sizes. Your permitted parameters should look like this: [[See Video to Reveal this Text or Code Snippet]] Make sure that you include variant_sizes_attributes nested inside variant_colors_attributes. This allows Rails to accept nested form inputs for sizes. Conclusion When working with double nested forms in Rails and Active Admin, it’s essential to structure your forms correctly and permit the right parameters in your controllers. By simplifying your form structure and ensuring the right nested attributes are permitted, you can fix rendering issues effectively. By following these steps, you should now be able to see the variant_sizes form fields appear correctly under each variant_colors entry in your Active Admin interface. Happy coding!