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.

• 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 Avo::Resources::SuperUser should receive the underlying model_class so Avo knows which model it represents.

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

  def fields
    field :id, as: :id
    field :name, as: :text
  end
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 Avo::Resources::Person to list all the records, but when your user clicks on a person, you want to use the inherited resources (Avo::Resources::Sibiling and Avo::Resources::Spouse) 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 Avo::Resources::Person 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: false Use it on a has_many field. On the Avo::Resources::Person 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.