Associations

One of the most amazing things about Ruby on Rails is how easy it is to create Active Record associations between models. We try to keep the same simple approach in Avo too.

WARNING

It's important to set the inverse_of as often as possible to your model's association attribute.

• Belongs to
• Has one
• Has many
• Has many through
• Has and blongs to many

Single Table Inheritance (STI)

When you have models that share behavior and fields with STI, Rails will cast the model as the final class no matter how you query it.

# app/models/user.rb
class User < ApplicationRecord
end

# app/models/super_user.rb
class SuperUser < User
end

# User.all.map(&:class) => [User, SuperUser]

For example, when you have two models, User and SuperUser with STI, when you call User.all, Rails will return an instance of User and an instance of SuperUser. That confuses Avo in producing the proper resource of User. That's why when you deal with STI, the final resource SuperUserResource should receive the underlying model_class so Avo knows which model it represents.

class SuperUserResource < Avo::BaseResource
  self.title = :name
  self.includes = []
  self.model_class = ::SuperUser

  field :id, as: :id
  field :name, as: :text
end

Link to child resource when using STI

Let's take another example. We have a Person model and Sibling and Spouse models that inherit from it.

You may want to use the PersonResource to list all the records, but when your user clicks on a person, you want to use the inherited resources (SiblingResource and SpouseResource) to display the details. The reason is that you may want to display different fields or resource tools for each resource type.

There are two ways you can use this:

1. self.link_to_child_resource = true Declare this option on the parent resource. When a user is on the Index view of your the PersonResource and clicks on the view button of a Person they will be redirected to a Child or Spouse resource instead of a Person resource.
2. field :peoples, as: :has_many, link_to_child_resource: true Use it on a has_many field. On the PersonResource you may want to show all the related people on the Show page, but when someone click on a record, they are redirected to the inherited Child or Spouse resource.

Add custom labels to the associations' pages

You might want to change the name that appears on the association page. For example, if you're displaying a team_members association, your users will default see Team members as the title, but you'd like to show them Members.

You can customize that using fields localization.