Rails - Aug 2006 - Accessing Constants Declared in Helper Modules

Hello all,

I''m having great trouble accessing a constant declared in a helper for 
one of my view templates. I am trying to create a grouped selection list 
based on a predefined set of values. Rather than declare this set of 
values in the view, I wanted to put it in the helper that automatically 
gets included for the view. Unfortunately, it doesn''t seem to work.

All methods declared in the helper seem to work when called from the 
view, but any referenced constants spit out a NameError and Rails tells 
me I have an unitialized constant. I can get around this by referencing 
the constant explicitly like this: `MyHelperName::CONSTANT`, but this 
seems to defeat the elegance of using helpers in the first place.

My current solution is to wrap the constant in a method defined in the 
helper file. Is there a way around this? I noticed this ticket 
(http://72.14.209.104/search?q=cache:s1V2CcSpQDAJ:dev.rubyonrails.org/ticket/1790+rails+ticket+1790&hl=en&gl=us&ct=clnk&cd=1&client=safari)
describing what seems to be my problem, but it was posted a year ago and 
I''m currently running Rails 1.1.6.

Is this a known bug? Am I doing something wrong? I was trying to follow 
the example in AWDWR (2nd ed., Version: 2006-7-21, p.480), but I can''t 
seem to get it to work.

Any thoughts would be greatly appreciated!

Best wishes,
SD


-- 
Posted via http://www.ruby-forum.com/.

If app/helpers/application_helper.rb contains

     module ApplicationHelper
         MYCONST="Change"

then

     <%= ApplicationHelper.get_cost :MYCONST %>

will print "Change".

It''s in the documentation for class "Module" in the pickaxe
book.

www-data wrote:
> Hello all,
>
> I''m having great trouble accessing a constant declared in a helper
for
> one of my view templates. I am trying to create a grouped selection list 
> based on a predefined set of values. Rather than declare this set of 
> values in the view, I wanted to put it in the helper that automatically 
> gets included for the view. Unfortunately, it doesn''t seem to
work.
>
> All methods declared in the helper seem to work when called from the 
> view, but any referenced constants spit out a NameError and Rails tells 
> me I have an unitialized constant. I can get around this by referencing 
> the constant explicitly like this: `MyHelperName::CONSTANT`, but this 
> seems to defeat the elegance of using helpers in the first place.
>
> My current solution is to wrap the constant in a method defined in the 
> helper file. Is there a way around this? I noticed this ticket 
>
(http://72.14.209.104/search?q=cache:s1V2CcSpQDAJ:dev.rubyonrails.org/ticket/1790+rails+ticket+1790&hl=en&gl=us&ct=clnk&cd=1&client=safari)
> describing what seems to be my problem, but it was posted a year ago and 
> I''m currently running Rails 1.1.6.
>
> Is this a known bug? Am I doing something wrong? I was trying to follow 
> the example in AWDWR (2nd ed., Version: 2006-7-21, p.480), but I
can''t
> seem to get it to work.
>
> Any thoughts would be greatly appreciated!
>
> Best wishes,
> SD
>
>
>   
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Thanks for the reply, Robert. What I''m trying to do, however, is not 
have to refer to the namespace where the constant is declared. I thought 
the idea of a helper such as app/helpers/my_helper.rb is that its 
methods and constants are included in app/controllers/my_controller.rb.

I was actually trying to use the example given in AWDWR (2nd ed., 
Version: 2006-7-21) on p.480, the code for which is here:

- 
http://media.pragprog.com/titles/rails2/code/e1/views/app/helpers/test_helper.rb
- 
http://media.pragprog.com/titles/rails2/code/e1/views/app/views/test/select.rhtml

The code in the view looks like this:

  <%    option_groups_from_collection_for_select(SHIPPING_OPTIONS,
    :options, :type_name, # <- groups
    :id,:name, # <- items
    @order.shipping_option)
  %>

Note how the SHIPPING_OPTIONS constant is referred to without prefixing 
it with the helper module''s namespace.

I wanted to have something like that. Any thoughts?

Best wishes,
SD


-- 
Posted via http://www.ruby-forum.com/.

Perhaps the difference in the test framework is that there''s a module 
include or extend somewhere behind the scenes?




www-data wrote:
> Thanks for the reply, Robert. What I''m trying to do, however, is
not
> have to refer to the namespace where the constant is declared. I thought 
> the idea of a helper such as app/helpers/my_helper.rb is that its 
> methods and constants are included in app/controllers/my_controller.rb.
>
> I was actually trying to use the example given in AWDWR (2nd ed., 
> Version: 2006-7-21) on p.480, the code for which is here:
>
> - 
>
http://media.pragprog.com/titles/rails2/code/e1/views/app/helpers/test_helper.rb
> - 
>
http://media.pragprog.com/titles/rails2/code/e1/views/app/views/test/select.rhtml
>
> The code in the view looks like this:
>
>   <%>     option_groups_from_collection_for_select(SHIPPING_OPTIONS,
>     :options, :type_name, # <- groups
>     :id,:name, # <- items
>     @order.shipping_option)
>   %>
>
> Note how the SHIPPING_OPTIONS constant is referred to without prefixing 
> it with the helper module''s namespace.
>
> I wanted to have something like that. Any thoughts?
>
> Best wishes,
> SD
>
>
>   
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Dear Robert,

Thanks again for the reply. Unfortunately, to the best of my knowledge, 
there''s nothing magical going on behind the scenes. So, I''m
stumped.
Even when I try my code with an explicit "include", I still
can''t
reference the constant without getting an error.

I hope I am just being stupid and missing something simple, but I can''t
work out what it might be!

Hopefully someone else can pick up on this and provide some input.

Best wishes,
SD


-- 
Posted via http://www.ruby-forum.com/.