Question

I’m trying to set up a model using UUIDs instead of auto-increment. Without bothering with the UUID part, here is what my code looks like:

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users, :id => false do |t|
      t.column :id, 'char(36) binary', :null => false, :primary => true
      t.string :email
      t.string :username
      t.string :password_hash
      t.string :password_salt

      t.timestamps
    end
  end
end

The user model just has:

class User < ActiveRecord::Base
end

When I try to assign the id in the console it doesn’t take:

ruby-1.9.3-p0 > u = User.new
 => #<User id: nil, email: nil, username: nil, password_hash: nil, password_salt: nil, created_at: nil, updated_at: nil> 
ruby-1.9.3-p0 > u.id = 'stuff'
 => "stuff" 
ruby-1.9.3-p0 > u.id
 => nil 
ruby-1.9.3-p0 > u.id = UUIDTools::UUID.random_create.to_s
 => "d3cd5bef-22b4-4fb1-b00f-10d8bbc94dc1" 
ruby-1.9.3-p0 > u.id
 => nil 
ruby-1.9.3-p0 > u.email = 'stuff'
 => "stuff" 
ruby-1.9.3-p0 > u.email
 => "stuff"

Why can I not assign the id manually? If I name the column something else it works, but I’d prefer to be able to use the id field so I don’t have to override all the rails magic. It seems to work fine in Rails 2. Is there some Rails setting that protects the id from changes?

Answer 1

Try using this:

set_primary_key :id

in your models.

There’s also a activeuuid plugin.

This SO post seems to back up the set_primary_key thing, at least partially.