Question

I have two tables: groups and series. A serie has_many groups and a group belongs_to a serie.
I’m using Formstastic to automatically generate a <select> with all the series so the user will be able to select the serie related to the group being created.
But a serie belongs_to the table units, which has_many series. Since series have the same name, it will not possible for the user to know exactly which serie he’s choosing in the <select>, unless he knows to which unit a specific serie belongs to. For that I’d like every <option> to have the following format:

<option value="serie_id">serie.name – unit.name</option>

What I have until now (and working) is:

ActiveAdmin.register Group do

  form do |f|
    f.inputs "Group" do       
        f.input :serie
        f.input :name
    end                               
  f.actions                         
  end 
end

Any other suggestion on how to achieve my goal (specifying exactly the serie related to the unit) will be appreciated.

Answer 1

Try the following:

# in controller
@custom_collection = Serie.all.map{ |s| ["#{s.name} - #{s.unit.name}", s.id]}

# in view
f.input :serie, collection: options_for_select(@custom_collection)

This code assumes that a Serie always have a Unit associated. It will raise an error if not. Use the following if you want to show the unit name only if it exists:

@custom_collection = Serie.all.map do |serie|
  composed_name = s.name
  composed_name += " - #{s.unit.name}" if s.unit.present?
  [composed_name, s.id]
end