Can't read the data from 2nd level nested attribute in ActiveAdmin

Question

I have 3 classes:

app/model/order.rb

class Order < ActiveRecord::Base
    has_many :lines, dependent: :destroy
    accepts_nested_attributes_for :lines, allow_destroy: true
end

app/model/line.rb

class Line < ActiveRecord::Base
  belongs_to :order
  has_many :picklines, dependent: :destroy
end

app/model/pickline.rb

class Pickline < ActiveRecord::Base
  belongs_to :line
end

So, from the above, the structure as follows Order>Line>Pickline, i.e. Pickline will be 2nd level nested attrubte to Order.

I was able to read the column from Line (1st level nested) as below:

app/admin/order.rb

show do
   panel "Items" do
      table_for order.lines do
        column :description
      end
   end
end

Now, I'm having headache on how to retrieve, for example, column named "quantity" from the 2nd level nested attribute of Pickline...

I understand that I first have to iterate on each Line and then on each Pickline to retrieve any column from Pickline, but can't figure out how this can be done in ActiveAdmin.

Answer 1

2 options

1) you can use block inside column method

show do
   panel "Items" do
      table_for order.lines do
        column :description
        column :quantity do |line|
            line.picklines.count #<-- you can access picklines for each line here
        end
      end
   end
end

2) Try to use has_many :through

http://guides.rubyonrails.org/association_basics.html#the-has-many-through-association

The has_many :through association is also useful for setting up "shortcuts" through nested has_many associations.

class Order < ActiveRecord::Base
    has_many :lines, dependent: :destroy
    has_many :picklines, through: :lines #<---- this line  
    accepts_nested_attributes_for :lines, allow_destroy: true
end

Than you can iterate over picklines

show do
   panel "Picklines" do
      table_for order.picklines do 
        column :description do |row|
            row.line.description
        end
        column :quantity  
      end
   end
end