ActiveAdmin and FriendlyId are both handy gems, but they don’t play nice together out of the box.

This is because FriendlyId‘d models don’t follow the default to_param style of id-based lookups which ActiveAdmin expects.

However, the two are easily reconciled by changing how ActiveAdmin fetches resources. Throw this in your ActiveAdmin initializer:

# config/initializers/active_admin.rb
ActiveAdmin::ResourceController.class_eval do
  def find_resource
    id_field = "id"

    if scoped_collection.is_a? FriendlyId
      id_field = scoped_collection.friendly_id_config.query_field

    scoped_collection.find_by! id_field => params[:id]

That’ll do it. You can alternatively define find_resource inside each registered resource’s controller block if you want to be picky.

There may be a better way to derive the id_field, but I don’t know it. Let me know if you do.