Formatting issue in ActiveAdmin dashboard

Question

I'm having an issue pulling the correct information into a dashboard column using ActiveAdmin. If anyone could help me wrap my head around this issue it would be greatly appreciated.

The issue I'm having is retaining the data from an associated class with the current record I'm displaying (line 6 below).

Here is the column I've created:

  column do
    panel "Recent Beacons" do
      table_for Beacon.limit(20) do
        column("Mac address") { |b| link_to b.mac_address, admin_beacon_path(b) }
        column "Last seen", :updated_at
        column("House") { |b| link_to b.root_house, admin_house_path(b.root_house.id) }
        column("Status") { |b| b.online? ? status_tag('Online', :green) : status_tag('Offline', :red) }
      end
    end
  end

Using binding.pry I'm able to perform a b.meters.pop.circuit.root and return the correct value I'm looking for. However it ActiveAdmin doesn't like this and the page errors with the following undefined method circuit for nil:NilClass. Trying to clean up the code a bit I wrote a root_house method.

  def root_house
    meters.pop.circuit.root
  end

ActiveAdmin has left me a bit confused and any help is greatly appreciated.

Thanks!

Answer 1

Here's a dirty fix for this, refactor as you wish:

  def root_house
    if meters && meters.pop && meters.pop.circuit
      meters.pop.circuit.root
    else
    'object is not present'
    end
  end

So I'm only going to call meters.pop.circuit.root if meters and meters.pop and meters.pop.ciruit is not nil.

Google null object pattern and law of Demeter ruby for a cleaner solution, also you can use delegate method, this might be helpful.