Application wide values/code

Rails
1

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

2

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

3

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. [email protected]

4

Quoting pepe [email protected]:

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

5

Thanks a lot Jeffrey.

Pepe

On Aug 28, 11:05 am, “Jeffrey L. Taylor” [email protected]