Rails Constant and Global Variables（Rails的常量和全局变量）

最新推荐文章于 2020-07-21 14:37:29 发布

转载最新推荐文章于 2020-07-21 14:37:29 发布 · 103 阅读

本文介绍在Rails应用中如何定义全局变量和常量，包括不同环境下的配置方法。阐述了将这些变量放置在config/environment.rb文件中的原因，并提到了特定于环境的变量应放在各自的环境配置文件中。

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在Rails下定义常量和全局变量的方法如下，如果你希望任何环境（开发，测试，产品）下都可以访问的话，则定义在config/environment.rb中
如：
BOOLEN_TRUE=1
如果你希望你的全局变量根据环境来决定，则根据需要在下面的环境中配置
/config/environments/development.rb
/config/environments/test.rb
/config/environments/production.rb

注意，
1> 常量和全局变量必须全部为大写；
2> 设置了全局常量和变量后需重新启动服务器以加载新的设置。

PS. english version

I was recently faced with a common problem that I wanted to share. During development there are times you need to specifiy a global or constant variable that will be shared throughout the entire application. In ColdFusion you would normally place something like this in Application.cfm. In Rails I was uncertain how exactly to approach this. At first I thought an application.rb file made sense, but the more I thought about it I decided to take advantage of the config files.

Since my global variable was one that would be consistent regardless of environment (dev, test, and prod) I decided to place it in config/environment.rb. I placed this under the RAILS_GEM_VERSION constant:

# Specifies gem version of Rails to use when vendor/rails is not present
RAILS_GEM_VERSION = ‘1.1.2′
BASE_URL = ‘http://mydomain.com/’

Now referencing this in any view can be done similar to any other variable:

<%= BASE_URL %>

If you need to specify globals that are specific to environment then I recommend placing them in their appropriate config file:

/config/environments/development.rb
/config/environments/test.rb
/config/environments/production.rb

From: http://www.db75.com/new_blog/?p=262