# Application wide values/code

**URL:** <https://www.ruby-forum.com/t/application-wide-values-code/147022>\
**Category:** Rails\
**Created:** [August 27, 2008, 5:36pm UTC](https://www.ruby-forum.com/t/application-wide-values-code/147022 "2008-08-27T17:36:29Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![pepe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@pepe](https://www.ruby-forum.com/u/pepe)\
**Post date:** [August 27, 2008, 5:36pm UTC](https://www.ruby-forum.com/t/application-wide-values-code/147022/1 "2008-08-27T17:36:29Z")

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Hello,

I know this is going to be very simple but I am new enough to not have  
it very clear.

If I wanted to have values/constants and code available in all parts  
of the application (views, controllers and models), where should I put  
them?

And a bonus question, I have noticed that session values are not  
available in the models. Is there a reason for that or maybe I am not  
smart enough to figure it out?

Thank you.

Pepe

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**Author:** ![pepe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@pepe](https://www.ruby-forum.com/u/pepe)\
**Post date:** [August 27, 2008, 5:54pm UTC](https://www.ruby-forum.com/t/application-wide-values-code/147022/2 "2008-08-27T17:54:29Z")

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> I know this is going to be very simple but I am new enough to not have  
> it very clear.
> 
> If I wanted to have values/constants and code available in all parts  
> of the application (views, controllers and models), where should I put  
> them?  
> Actually, that’s not such a simple question, because it depends a lot on  
> the data you want to provide. Typically this type of information is  
> provided in the session hash. In fact that’s one purpose of the session  
> hash.

In an object oriented applications global variables are generally  
considered evil and should be avoided.

Constants are already available anywhere in your application through the  
namespace of the class.

If you had:

class MyClass  
MY\_CONSTANT = “Whatever”  
end

You would access that constant with MyClass::MY\_CONSTANT. Notice the  
namespace operator “::” used.

> And a bonus question, I have noticed that session values are not  
> available in the models. Is there a reason for that or maybe I am not  
> smart enough to figure it out?  
> This is by design. It is, technically, a violation of MVC to make  
> session variables available in model objects. This would create a tight  
> coupling between the model and the view/controller. MVC is designed to  
> prevent that.

Model objects should be reusable apart from their view/controller.  
Depending on a session variable in your model would break that  
reusability. At least that’s the theory. In practice there are ways  
around this, but I wouldn’t personally recommend them unless you have no  
other choice.

Generally speaking, if you are feeling the need to access session data  
in a model, chances are you’re doing something wrong. A proper  
encapsulated and decoupled solution should be sought in those cases.

pepe wrote:

> Hello,
> 
> I know this is going to be very simple but I am new enough to not have  
> it very clear.
> 
> If I wanted to have values/constants and code available in all parts  
> of the application (views, controllers and models), where should I put  
> them?
> 
> And a bonus question, I have noticed that session values are not  
> available in the models. Is there a reason for that or maybe I am not  
> smart enough to figure it out?
> 
> Thank you.
> 
> Pepe

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<div class="post-metadata">

**Author:** ![pepe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@pepe](https://www.ruby-forum.com/u/pepe)\
**Post date:** [August 28, 2008, 4:59pm UTC](https://www.ruby-forum.com/t/application-wide-values-code/147022/3 "2008-08-28T16:59:26Z")

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Thanks a lot, Robert.

The explanation about the MVC design makes absolute sense. The way I  
am going around the session values is by passing variables to the  
methods I need to execute in the models. I was curious as of why the  
session values were not available there.

I already knew about the MyClass::MY\_CONSTANT way of accessing the  
values but I wasn’t sure if there was another, “simpler” way by which  
those values can be accessed. If there is no “simpler” way, where  
should I put my class with my constant definitions then and would I  
need to require the class in my controller and models?

Thanks a lot.

Pepe

On Aug 27, 11:54 am, Robert W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

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<div class="post-metadata">

**Author:** ![pepe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@pepe](https://www.ruby-forum.com/u/pepe)\
**Post date:** [August 28, 2008, 5:06pm UTC](https://www.ruby-forum.com/t/application-wide-values-code/147022/4 "2008-08-28T17:06:28Z")

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Quoting pepe [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> those values can be accessed. If there is no “simpler” way, where  
> should I put my class with my constant definitions then and would I  
> need to require the class in my controller and models?

If they truly are application wide, put them in a Ruby file in the  
config/initializers/ directory. This feature was introduced in 2.X,  
IIRC.  
Where X is in the range 0 to 1, IDRW (I Don’t Recall Which).

Or in prior versions at the bottom of config/environment.rb

HTH,  
Jeffrey

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<div class="post-metadata">

**Author:** ![pepe](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/4da419/32.png) [@pepe](https://www.ruby-forum.com/u/pepe)\
**Post date:** [August 29, 2008, 6:35pm UTC](https://www.ruby-forum.com/t/application-wide-values-code/147022/5 "2008-08-29T18:35:09Z")

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Thanks a lot Jeffrey.

Pepe

On Aug 28, 11:05 am, “Jeffrey L. Taylor” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)