nested object formsのcheckbox使用例

nested object formは以下のrailscast動画を見れば把握できます

• #196 Nested Model Form Part 1
• #197 Nested Model Form Part 2

チェックボックスを使用するときはちょっとめんどくさかったのでメモ

基本

Article model

class Article < ActiveRecord::Base
  attr_accessible :articles_categories_attributes

  has_many :categories, :through => :articles_categories
  has_many :articles_categories, :dependent => :destroy

  accepts_nested_attributes_for :articles_categories, :allow_destroy => true
end

ArticlesCategory model

class ArticlesCategory < ActiveRecord::Base
  attr_accessible :article_id, :category_id

  belongs_to :article
  belongs_to :category
end

Category model

class Category < ActiveRecord::Base
  attr_accessible :name

  has_many :articles, :through => :articles_categories
  has_many :articles_categories, :dependent => :destroy
end

view、update method

view

<% Category.all.each do |category| %>

  <% check_flag = @article.articles_categories.any? { |articles_category| articles_category.category_id == category.id } %>

  <%= check_box_tag "article[articles_categories_attributes][][category_id]", category.id, check_flag %>
  <%= category.name %>
<% end %>

update method

def update
  ArticlesCategory.transaction do
    @article = Article.find(params[:id], :lock => true)
    @article.articles_categories.clear
    @article.update_attributes!(params[:interview_article])
  end
    flash[:notice] = 'Article was successfully updated.'
    redirect_to :action => 'index'
    rescue ActiveRecord::RecordInvalid
    render :action => 'edit'
end