Edit relationship of parent record in activeadmin

Question

I have the following model structure:

• Composition has many Score (Score belongs to Composition)
• Composition has and belongs to many Countries (and viceversa)

score.rb:

class Score < ApplicationRecord
  belongs_to :composition
end

composition.rb:

class Composition < ApplicationRecord
  has_many :scores
  has_and_belongs_to_many :countries, join_table: :rights_countries
end

country.rb:

class Country < ApplicationRecord
  has_and_belongs_to_many :compositions, join_table: :rights_countries
end

In activeadmin, I want to be able to edit the countries of a composition, but in the edit form of its scores.

Of course, the form will import this data from composition, and default inputs will be equal for all the scores (children) of a composition.

I found no way to implement this in activeadmin up to now.

Is this even possible? If yes, is the solution easy or cumbersome?

Answer 1

Following this link, I added an inputs within an inputs and updated the corresponding params. I also added accepts_nested_attributes_for :composition in the score model.

app/models/score.rb

...
accepts_nested_attributes_for :composition
...

app/admin/score.rb

...
permit_params ...,
              composition_attributes: [:id, country_ids: []]
...
form do |f|
  f.inputs do
    ...
    f.inputs "", for: [:composition, score.composition] do |c|
      c.input :countries, as: :select, collection: Country.order_by_name.uniq.map { |p| [p.name, p.id] }
    end
  end
end

Let me know if there's a cleaner solution.