Comparison between the DataMapper gem and the ActiveRecord gem

active_record_store.rb

class Store < ActiveRecord::Base
  has_many :products
  belongs_to :user
 
  validates_presence_of :name
end

> Store.create(:name => "Amazon")
> Store.where(:name => "Amazon")

data_mapper_store.rb

class Store
  include DataMapper::Resource
  
  property :id, Serial
  property :name, String

  has n, :products
  belongs_to :user

  validates_presence_of :name
end

> Store.create(:name => "Apple")
> Store.all(:name => "Apple")

Thanks @dukbb, I have fixed that.