Best Practice for Helper/Partial that render a Model driven select - ruby-on-rails

Question

Let's assume I have a model Product, and I want a drop-down select box that contains all products. This drop-down is used in several views, so it is going to be created by a helper method. Where is the 'best practice' location to get the select options from Product? Do I set #products = Product.all in every controller action that needs to show the drop-down, or do I make the helper method self contained by having it call Product.all? Does the answer change if I am dealing with a partial, or if I am filtering the products (i.e. Product.in_category(#category))? MVC says use the controller, but DRY says use the helper.

Answer 1

Look at the collection_select form helper that's built in. You can pass in different collections (Product.all, Product.) as and where needed in different views.
collection_select
From the link:
collection_select(object, method, collection, value_method,
text_method, options = {}, html_options = {})
Returns and tags for the collection of existing
return values of method for object‘s class. The value returned from
calling method on the instance object will be selected. If calling
method returns nil, no selection is made without including :prompt or
:include_blank in the options hash.
The :value_method and :text_method parameters are methods to be called
on each member of collection. The return values are used as the value
attribute and contents of each tag, respectively. They can
also be any object that responds to call, such as a proc, that will be
called for each member of the collection to retrieve the value/text.
Example object structure for use with this method:
class Post < ActiveRecord::Base belongs_to :author end
class Author < ActiveRecord::Base has_many :posts def
name_with_initial
"#{first_name.first}. #{last_name}" end end
Sample usage (selecting the associated Author for an instance of Post,
#post):
collection_select(:post, :author_id, Author.all, :id,
:name_with_initial, prompt: true)
If #post.author_id is already 1, this would return:
Please
select D. Heinemeier
Hansson D. Thomas M. Clark

Answer 2

In my opinion, Controller should decide what data the user sees. How the user sees it can be decided by the view or by the helper.
So i would advise you to put
#products = Product.all
or
Product.in_category(#category)
in your controller
Any kind of filter you apply should be done in the controller as well

Answer 3

With rails being a model-view-controller (MVC) framework, you're going to want that logic to be on the model. Having some method that returns the options for your select would probably be best (though, take that with a grain of salt because these things change a lot with application). Something I might try would be along the lines of:
class Product < ActiveRecord::Base
def self.get_select_options(category=nil)
if category.nil?
Product.all
else
Product.in_category(category)
end
end
end
... which you could then call with Product.get_select_options or Product.get_select_options(#category)