Where to store globally shared data structures in Rails

Question

I have a data structure like this in one of my models:

def image_size_limits
    {
        "web" => {"maxheight" => 480, "maxwidth" => 680, "minheight" => 400, "minwidth" => 600}, 
        "phone" => {"height" => 345, "width" => 230, "minheight" => 300, "minwidth" => 200},
        "tablet" => {"height" => 680, "width" => 480, "minheight" => 600, "minwidth" => 400},
        "other" => {"height" => 680, "width" => 480, "minheight" => 600, "minwidth" => 400}
    }
end

I use this in a custom validator I have to validate the sizes of images uploaded. I would like to be able to use this data structure not just in this one model - but everywhere. In all my models, views and controllers.

How would I go about doing that, where would I put it?

score 2 · Accepted Answer · edited May 23 '17 at 12:29

I would use a module.

Stick it in your lib directory. (You may need to configure Rails 3 to autoload classes and modules from your lib folder. See this question.)

# lib/image_sizes.rb

module ImageSizes
  def image_size_limits
    {
      "web" => {"maxheight" => 480, "maxwidth" => 680, "minheight" => 400, "minwidth" => 600}, 
      "phone" => {"height" => 345, "width" => 230, "minheight" => 300, "minwidth" => 200},
      "tablet" => {"height" => 680, "width" => 480, "minheight" => 600, "minwidth" => 400},
      "other" => {"height" => 680, "width" => 480, "minheight" => 600, "minwidth" => 400}
    }
  end
end

Then in your models or controllers:

class MyModel < ActiveRecord::Base
  include ImageSizes
  # ...
end


class MyController < ApplicationController
  include ImageSizes
  # ...
end

Now, each model or controller that includes the ImageSizes module will have access to the module's methods, namely image_size_limits.

In Rails 4, there will also be concerns. Check this out: http://railscasts.com/episodes/400-what-s-new-in-rails-4 — Dennis Hackethal, Apr 10 '13 at 00:24

score 2 · Answer 2 · answered Apr 10 '13 at 01:02

Another option is to create an initializer file and declare a constant there.

# config/initializers/image_size_limits.rb

IMAGE_SIZE_LIMITS = {
  "web" => {"maxheight" => 480, "maxwidth" => 680, "minheight" => 400, "minwidth" => 600}, 
  "phone" => {"height" => 345, "width" => 230, "minheight" => 300, "minwidth" => 200},
  "tablet" => {"height" => 680, "width" => 480, "minheight" => 600, "minwidth" => 400},
  "other" => {"height" => 680, "width" => 480, "minheight" => 600, "minwidth" => 400}
}

Then in your model or controller, just use IMAGE_SIZE_LIMITS['web']['maxheight'] to get 480.

Where to store globally shared data structures in Rails

2 Answers2