Complex Forms

http://railscasts.com/episodes/73
http://railscasts.com/episodes/74
http://railscasts.com/episodes/75
http://api.rubyonrails.org/classes/ActionView/Helpers/PrototypeHelper/JavaScriptGenerator/GeneratorMethods.html#M001254
http://api.rubyonrails.org/classes/ActionView/Helpers/JavaScriptHelper.html#M001341

[View edit.rhtml]
<div id='books'>
 <%= render :partial => 'book', :collection => @user.books %>
</div>
<%= add_book_link 'add book'%>


[user helper]
module UsersHelper
def add_book_link(name)
    link_to_function name do |page|
      page.insert_html :bottom, :books, :partial => 'book', :object => Book.new
    end
end
end

[View book partial]

<% fields_for "user[books][]", book do |b| %>
<%= b.text_field :name %>
<%= link_to_function 'remove', "this.up('.book').remove()"%>
<% end %>



下面是強化版

[view, edit.rhtml]
<div class='book'>
<% fields_for "user[books][]", book, :index => nil do |b| %>
  <%= b.text_field :name %>
  <% if book.new_record?%>
    <%= link_to_function 'remove', "this.up('.book').remove()" %><br /> <= 單純移掉 html, 反正是new出來的還沒存
  <% else %>
    <%= link_to_function 'remove', 'mark_for_destory(this)' %>
    <%= b.hidden_field :id %>           <= 原有的 object 把 id藏起來
    <%= b.hidden_field :should_destroy, :class => 'should_destroy' %> <= 用來記真的要砍的記號
  <% end %>
<% end %>
</div>


[js application.js]
function mark_for_destory(element) {
 $(element).next('.should_destroy').value = 1;   <= 做了記號後
 $(element).up('.book').hide();                           <= 藏起來
}

[Controller, user_controller.rb]
@user.update_attributes(params[:user])

[Model book.rb]
 attr_accessor :should_destroy

 def should_destroy?
   should_destroy.to_i == 1
 end

[Model user.rb]
 after_update :save_books

 def books=(books_attrs)
    books_attrs.each do |attrs|
      if attrs[:id].blank?          <= 如果id是空的就是需要new的
        books.build(attrs)
       else
        book = books.detect{|b| b.id == attrs[:id].to_i}
        book.attributes = attrs   <= 這時上面那些有被destroy 的 should_destroy 也會被給值
      end
    end
 end

 def save_books   <= parent object update_attribute would not update the children attribute, so we need to save by ourself
   books.each do |book|
     if book.should_destroy?
       book.destroy
     else
       book.save # if Calling save(false) saves the model without running validations.
     end
   end
 end