Base-camp Style Subdomains and IDs of Models

I have an app that has Basecamp-style subdomains, that is, I have Projects, Users, Apples and Oranges. The Users, Apples and Oranges are all keyed to a Project and only exist in the http://project.myapp.com. I added a project_id to Users, Apples and Oranges and everything works, except of course that the ids of those three objects increment globally, and throughout my app I lookup objects by that id.

This doesn't seem lik开发者_StackOverflowe best practice. Should I instead do lookups by a secondary key? How does that affect efficiency? If there's a good blog post that covers this, would be wesome.

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It is ok to have a global id (in the database). If possible, don't show those database ids, use friendly urls instead.

Anyways, you shouldn't trust your users: even if you have the id, check if the record is associated with the project.

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In your controllers just scope everything to a Project, assuming a Project has_many :apples:

class ApplesController < ApplicationController
  before_filter :find_apple

  private
    def find_apple
      if current_user.is_admin?
        @apple = Apple.find(params[:id])
      else
        # Scope to the current project/subdomain
        # Note the use of current_project
        # You need to exchange this with whatever you use to get the project object
        @apple = current_project.apples.find(params[:id])

        # Do something here if @apple is nil, like redirect
      end
    end
end