rails dynamic attributes

Question

I'd like to have a number of dynamic attributes for a User model, e.g., phone, address, zipcode, etc., but I would not like to add each to the database. Therefore I created a separate table called UserDetails for key-value pairs and a belongs_to :User.

Is there a way to somehow do something dynamic like this user.phone = "888 888 8888" which would essentially call a function that does:

UserDetail.create(:user => user, :key => "phone", :val => "888 888 8888")

and then have a matching getter:

def phone  
    UserDetail.find_by_user_id_and_key(user,key).val
end

All of this but for a number of attributes provided like phone, zip, address, etc., without arbitrarily adding a ton of of getters and setters?

Answer 1

You want to use the delegate command:

class User < ActiveRecord:Base
  has_one :user_detail
  delegate :phone, :other, :to => :user_detail
end

Then you can freely do user.phone = '888 888 888' or consult it like user.phone. Rails will automatically generate all the getters, setters and dynamic methods for you

Answer 2

You could use some meta-programming to set the properties on the model, something like the following: (this code was not tested)

class User < ActiveRecord:Base
  define_property "phone"
  define_property "other"
  #etc, you get the idea


  def self.define_property(name)
    define_method(name.to_sym) do
      UserDetail.find_by_user_id_and_key(id,name).val
    end
    define_method("#{name}=".to_sym) do |value|
      existing_property = UserDetail.find_by_user_id_and_key(id,name)
      if(existing_property)
        existing_property.val = value
        existing_property.save
      else
        new_prop = UserDetail.new
        new_prop.user_id = id
        new_prop.key = name
        new_prop.val = value
        new_prop.save
      end
    end
  end