Handle Multiple Models in One Form Handle Multiple Models in One Form

http://www.pragprog.com/titles/fr_arr/advanced-rails-recipes
http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#M001198

Recipe 13

[View, edit.rhtml]
<% form_for(@user) do |f| %>
  <%= f.text_field :name %>
  <% for book in @user.books %>
    <% fields_for "user[books][]", book do |b| %> <= 用fields_for的方法注意
      <%= b.text_field :name %>
    <% end %>
  <% end %>
    <%= f.submit "Update" %>
<% end %>

[user controller, update action]
  def update
    @user = User.find(params[:id])

      if @user.update_attributes(params[:user])
        flash[:notice] = 'User and books was successfully updated.'
        redirect_to(@user)
      end

    params[:user] 是長像這樣的東西 {"name"  => "ilake",
                                    "books" => {"1"=>{"name"=>"book1"}, "2"=>{"name"=>"book2"}}}
    update_attributes 就是去做 @user.name = 'ilake'
                               @user.books = {"1"=>{"name"=>"book1"}, "2"=>{"name"=>"book2"}} 的動作
  end

[user model]
class User < ActiveRecord::Base
  has_many :books, :dependent => :destroy
  has_one  :couple
  validates_presence_of :name

  after_update :save_books
     
  def books=(books_attrs)               <= 因為controller 的@user.update_attributes 被叫到
    books.reject(&:new_record?).each do |book|  <= 檢查這是不是新的record, 這邊是update 新的不要
      attributes = books_attrs[book.id.to_s]
      if attributes
        book.attributes = attributes
      else
        books.delete(book)
      end
    end
  end

  def save_books
    books.each do |book|
      book.save(false) # Calling save(false) saves the model without running validations.
    end
  end
end