Ruby on rails 如何检查是否定义了Rails.application.config变量?
即使Ruby on rails 如何检查是否定义了Rails.application.config变量?,ruby-on-rails,ruby,ruby-on-rails-4,Ruby On Rails,Ruby,Ruby On Rails 4,即使Rails.application.config.trackable_models返回一个完整的数组,defined?(Rails.application.config.trackable_models)返回零 Rails.application.config.trackable_models # => ["NewsItem", "ContentPage", "Event"] defined?(Rails.application.config.trackable_models): #
Rails.application.config.trackable_models
返回一个完整的数组,defined?(Rails.application.config.trackable_models)
返回零
Rails.application.config.trackable_models # => ["NewsItem", "ContentPage", "Event"]
defined?(Rails.application.config.trackable_models): # => nil
以相同的方式设置局部变量也可以:
foo = ["x"]
defined?(foo) # => local-variable
如果未“定义”,检查配置变量是否存在的正确方法是什么?如果要检查方法是按字面意义定义的,请使用
respond\u to
Rails.applications.config.respond_to?(:trackable_models)
如果要检查该方法是否返回非nil
的内容,可以使用以下选项:
tm = Rails.applications.config.trackable_models
tm.nil?
tm.presence || 'default value'
tm.present?
tm.blank?
谢谢@steel<代码>响应?工作正常。如果定义了可跟踪的_模型,则其余部分很有用,否则对
Rails.applications.config.trackable_模型的任何调用
都会导致“未定义的方法‘可跟踪的_模型’”