Rails Blog: Complex Nested Forms

We're going to build off the previous iteration of our Blog App, where we created new models for User and Tag (and applicable associations) and wrote validations. We want to clean up our tagging feature. Our ability to add tags to a new post is super useful, but what if, when we're making a new post, we want to add a new tag that isn't in the list? Let's build that out.

NOTE: As with much of our Rails curriculum, always use the --no-test-framework flag when generating models, controllers, etc. This prevents Rails generators from creating additional tests on top of the provided test suite. For example, use bin/rails generate model User username:string email:string --no-test-framework. This lab already includes starter files, so you do not need to generate tests.

Tags

1. We need to change the permitted params in our PostsController to accept another attribute, :tags_attributes, which contains the tag attributes that we need to create a new tag.

2. We also need an accepts_nested_attributes_for macro on our Post model, which will permit tags to be nested in our new Post form.

3. Now we can build a nested form in our Post form. Check out the documentation on Nested Forms for help.

4. We should be able to select previously created tags as well as create a new tag.

5. Remember, because we have a uniqueness validation on the name of tag, we will need to account for that.

6. A user shouldn't have to submit a new tag every time they submit a post.

   class User < ApplicationRecord
     has_many :posts
     accepts_nested_attributes_for :posts, reject_if: proc { |attributes| attributes['title'].blank? }
   end

7. To allow a user to create a new tag, the controller action for a new post should instantiate a new tag. Check out the documentation for the fields_for tag.

Resources

• Strong Params
• Nested Forms
• fields_for tag
• Preventing Empty Records