Rails.env与RAILS_ENV

Question

I see both in examples when checking what env one is running in. What's preferred? Are they, for all intents and purposes equal?

Answer 1

According to the docs , #Rails.env wraps RAILS_ENV :

    # File vendor/rails/railties/lib/initializer.rb, line 55
     def env
       @_env ||= ActiveSupport::StringInquirer.new(RAILS_ENV)
     end

But, look at specifically how it's wrapped, using ActiveSupport::StringInquirer :

Wrapping a string in this class gives you a prettier way to test for equality. The value returned by Rails.env is wrapped in a StringInquirer object so instead of calling this:

 Rails.env == "production" 

you can call this:

 Rails.env.production? 

So they aren't exactly equivalent, but they're fairly close. I haven't used Rails much yet, but I'd say #Rails.env is certainly the more visually attractive option due to using StringInquirer .

Answer 2

Before Rails 2.x the preferred way to get the current environment was using the RAILS_ENV constant. Likewise, you can use RAILS_DEFAULT_LOGGER to get the current logger or RAILS_ROOT to get the path to the root folder.

Starting from Rails 2.x, Rails introduced the Rails module with some special methods:

• Rails.root
• Rails.env
• Rails.logger

This isn't just a cosmetic change. The Rails module offers capabilities not available using the standard constants such as StringInquirer support. There are also some slight differences. Rails.root doesn't return a simple String buth a Path instance.

Anyway, the preferred way is using the Rails module. Constants are deprecated in Rails 3 and will be removed in a future release, perhaps Rails 3.1.

Answer 3

ENV['RAILS_ENV'] is now deprecated .

You should use Rails.env which is clearly much nicer.

Answer 4

Strange behaviour while debugging my app: require "active_support/notifications" (rdb:1) p ENV['RAILS_ENV'] "test" (rdb:1) p Rails.env "development"

I would say that you should stick to one or another (and preferably Rails.env)

Answer 5

更新：在Rails 3.0.9中：在railties / lib / rails.rb中定义的env方法