How do I check if a Rails.application.config variable is defined?

Question

Even though Rails.application.config.trackable_models returns a full array, defined?(Rails.application.config.trackable_models) returns nil.

Rails.application.config.trackable_models # => ["NewsItem", "ContentPage", "Event"]
defined?(Rails.application.config.trackable_models): # => nil 

Setting a local variable in the same way is fine:

foo = ["x"]
defined?(foo) # => local-variable

What is the proper way to check for the existence of a config variable if not "defined?"?

Answer 1

If you want to check the method is defined in the literal sense, use respond_to

Rails.application.config.respond_to?(:trackable_models)

If you want to check if the method returns something other than nil, you have some options:

tm = Rails.application.config.trackable_models
tm.nil?
tm.presence || 'default value'
tm.present?
tm.blank?