Feature Flags with Pundit

add_feature_flags_to_users.rb

# Migration...
class AddFeatureFlagsToUsers < ActiveRecord::Migration[5.2]
  def change
    add_column :users, :feature_flags, :string, array: true, default: []
  end
end

feature_policy.rb

FeaturePolicy = Struct.new(:user, :feature) do
  # Respond to any method ending with a question mark.
  # Look for a feature flag with that name in that user's record.
  #
  # It looks for an array attribute called `feature_flags` in the user's record, and checks to see if the requested feature is
  # included in the list of features.
  #
  # @example User can access accounting feature?
  #   policy(:feature).accounting?
  #
  # @return [Boolean]
  def method_missing(method_name, *params, &block)
    if respond_to_missing?(method_name)
      feature = method_name.to_s.parameterize
      user.feature_flags.include?(feature)
    else
      super
    end
  end

  private

  def respond_to_missing?(method_name, *)
    /^\w+\?/.match?(method_name)
  end
end