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PORails 3. Saving an association which attributes are represented by a value object
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2010-11-07T07:47:46.880
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Why can't I save changes in an associated object saving a current object if attributes of the first one are represented by a value object? For example, I have a simple e-commerce application. It use a Client model for manipulating clients Client model <pre> <code> # db/migrate/<...>_create_clients.rb class CreateClients < ActiveRecord::Migration def self.up create_table :clients do |t| t.string :name end end def self.down drop_table :clients end end </code> </pre> <pre> <code> # app/models/client.rb Client < ActiveRecord::Base has_one :balance end </code> </pre> and an associated Balance model for holding thier balances. Balance model <pre> <code> # db/migrate/<...>_create_balances.rb class CreateBalances < ActiveRecord::Migration def self.up create_table :balances do |t| t.integer :amount t.string :currency t.references :client end end def self.down drop_table :balances end end </code> </pre> <pre> <code> # app/models/balance.rb class Balance < ActiveRecord::Base belongs_to :client composed_of :money, :mapping => [%w{amount cents}, %w{currency currency_as_string}], :constructor => ->(amount, currency) { Money.new(amount || 0, currency || 'RUB') } end </code> </pre> The Balance model uses a Money object from an external library called <a href="http://money.rubyforge.org/index.html" rel="nofollow">Money</a>. The object represents model's attributes amount and currency adding to the model useful methods for manipulating those attributes. Gemfile <pre> <code> # Gemfile gem 'money' </pre> </code> I have some seed data in seeds.rb. Seeds <pre> <code> # db/seeds.rb elena = Client.create(:name => 'Elena') elena.build_balance.money = Money.new(0, 'RUB') elena.save </code> </pre> When I try to change a balance of the client it isn't changed in spite of the save method of the current object returns true. <pre> <code> >> elena = Client.find_by_name('Elena') => #<Client id: 1, name: "Elena"> >> elena.balance => #<Balance id: 1, amount: 0, currency: "RUB", client_id: 1> >> elena.balance.money => 0.00 >> elena.balance.money += Money.new(50000, 'RUB') => 500.00 >> elena.save => true # log/development.log # no changes </code> </pre> However, I can save the changes using the following two ways. 1. <pre> <code> >> elena = Client.find_by_name('Elena') => #<Client id: 1, name: "Elena"> >> balance = Balance.find(elena.id) => #<Balance id:1 , amount: 0, currency: "RUB", client_id: 1> >> balance.money += Money.new(50000, 'RUB') => 500.00 >> balance.save => true # log/development.log # UPDATE "balances" SET "amount" = 50000 WHERE ("balances"."id" = 1) </pre> </code> 2. <pre> <code> >> elena = Client.find_by_name('Elena') => #<Client id:1, name:"Elena"> >> elena.balance.money += Money.new(50000, 'RUB') => 500.00 >> elena.balance.save => true # log/development.log # UPDATE "balances" SET "amount" = 50000 WHERE ("balances"."id" = 1) </code> </pre> Despite I can save changes of a balance using the aforementioned ways I would like to know why I can't do it using the “traditional” <current_model>.save method. Thanks. Debian GNU/Linux 5.0.6; Ruby 1.9.2; Ruby on Rails 3.0.1; Money 3.1.5.
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<ruby-on-rails><associations><currency><aggregation>
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Rails 3. Saving an association which attributes are represented by a value object
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