application wide global variable

Question

In Rails, where should I define the variable which can be recognized by every layer of Rails stacks.

For example, I would like to have a CUSTOMER_NAME='John' variable which can be accessed in helper, rake task, controller and model. Where should I define this variable in Rails app?

I am using Rails v2.3.2

What you are asking about is not variable, but a constant, what means: it cannot be set from within application. I was misleaded here by search engine because the wrong term is used here. — Paul, May 27 '14 at 12:05

score 15 · Accepted Answer · answered Dec 02 '11 at 12:35

15

In an initializer in /app/config/initializers all .rb files in here get loaded, I usually create one called preferences.rb for things like this.

See: http://guides.rubyonrails.org/configuring.html#using-initializer-files

answered Dec 02 '11 at 12:35

Paul Groves

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score 15 · Answer 2 · answered Dec 02 '11 at 13:26

15

An alternative approach is to set a key on the config object in config/application.rb, like so:

MyApp::Application.configure do
   # ...
   config.my_key = 'some "global" value'
end

You can then access my_key from anywhere in your app with just this:

MyApp::Application.config.my_key

Also, Mike Perham has described a similar, though a more comprehensive approach in his blog post.

answered Dec 02 '11 at 13:26

Marek Příhoda

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Isn't that a constant but not variable? Could it be changed in an application during run time? – Paul Apr 10 '14 at 11:05
It's a variable and can be changed during runtime. – Oscar Barrett Aug 07 '14 at 07:09

score 9 · Answer 3 · answered Dec 02 '11 at 12:36

9

You want a true global constant? Use ::COSTUMER_NAME. You want a true global variable? Use $COSTUMER_NAME (discouraged). You want a request-global variable? Use the Hash in the #env method.

answered Dec 02 '11 at 12:36

Reactormonk

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You mean create a linux server wide global variable? – Mellon Dec 02 '11 at 12:45
1

`ENV` and `#env` are two different things. `ENV` is the global constant representing the Unix environment. `#env` is a controller method that returns the current rack environment. – Reactormonk Dec 02 '11 at 12:50
I do ::TESTABC = 'hola' and try to print from a view ::TESTABC and it says is not defined – Arnold Roa Jul 20 '14 at 18:48
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Why is $CUSTOMER_NAME discouraged ? – user1735921 Oct 06 '17 at 11:44
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`$CUSTOMER_NAME` is a process-global variable. `::COSTUMER_NAME` is a constant, so Ruby will at least complain when you reassign things to it. – Reactormonk Oct 06 '17 at 13:43

application wide global variable

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