Rails 4 嵌套表单字段未保存在数据库中

我有用于输入专辑以及属于专辑的歌曲的表格。专辑正在保存到数据库，但个别歌曲没有保存。

相册模型

class Album < ActiveRecord::Base
    belongs_to :user
    has_many :songs, :dependent => :destroy
    accepts_nested_attributes_for :songs
    has_attached_file :image, :styles => { :large => "500x500>", :medium => "300x300>", :thumb => "100x100>" }

    validates :image, presence: true
    validates :title, presence: true

    extend FriendlyId
    friendly_id :title, use: :slugged


end

歌曲模型

class Song < ActiveRecord::Base
    belongs_to :album

    extend FriendlyId
    friendly_id :title, use: :slugged
end

相册控制器

class AlbumsController < ApplicationController
  before_action :set_album, only: [:show, :edit, :update, :destroy]
  before_action :authenticate_user!, except: [:index, :show]
  before_filter :verify_is_admin, except: [:index, :show]


  def index
    @albums = Album.all.order("created_at DESC").paginate(:page => params[:page], :per_page => 8)
  end

  def show
  end

  def new
    @album = current_user.albums.build
    3.times { @album.songs.build }
  end

  def edit
  end

  def create
    @album = current_user.albums.build(album_params)
    if @album.save
      redirect_to @album, notice: 'Album was successfully created.'
    else
      render action: 'new'
    end
  end

  def update
    if @album.update(album_params)
      redirect_to @album, notice: 'Album was successfully updated.'
    else
      render action: 'edit'
    end
  end

  def destroy
    @album.destroy
    redirect_to albums_url
  end


  private

    def verify_is_admin
      (current_user.nil?) ? redirect_to(root_path) : (redirect_to(root_path) unless current_user.admin?)
    end

    # Use callbacks to share common setup or constraints between actions.
    def set_album
      @album = Album.find_by_slug(params[:id])
    end

    def correct_user
      @album = current_user.albums.find_by(id: params[:id])
      redirect_to albums_path, notice: "Not authorized to edit this album" if @album.nil?
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def album_params
      params.require(:album).permit(:title, :image, :embed, :embed_html)
    end
end

歌曲控制器

class SongsController < ApplicationController
  before_action :set_song, only: [:show, :edit, :update, :destroy]


  def index
    @songs = Song.all
  end

  def show
  end

  def new
    @song = Song.new
  end

  def edit
  end

  def create
    @song = Song.new(song_params)

    respond_to do |format|
      if @song.save
        format.html { redirect_to @song, notice: 'Song was successfully created.' }
        format.json { render action: 'show', status: :created, location: @song }
      else
        format.html { render action: 'new' }
        format.json { render json: @song.errors, status: :unprocessable_entity }
      end
    end
  end

  def update
    respond_to do |format|
      if @song.update(song_params)
        format.html { redirect_to @song, notice: 'Song was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: 'edit' }
        format.json { render json: @song.errors, status: :unprocessable_entity }
      end
    end
  end

  def destroy
    @song.destroy
    respond_to do |format|
      format.html { redirect_to songs_url }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_song
      @song = Song.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def song_params
      params.require(:song).permit(:title)
    end
end

这是新相册视图的表单

<%= form_for @album, html: { multipart: true } do |f| %>
  <% if @album.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@album.errors.count, "error") %> prohibited this album from being saved:</h2>

      <ul>
      <% @album.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="form-group">
    <%= f.label :Artwork %>
    <%= f.file_field :image, class: "form-control" %>
  </div>

  <div class="form-group">
    <%= f.label :title %>
    <%= f.text_field :title, class: "form-control" %>
  </div>

  <div class="form-group">
  <%= f.fields_for :songs do |builder| %>
    <fieldset>
      <%= builder.label :title, "Song" %><br />
      <%= builder.text_field :title, :rows => 3 %>
    </fieldset>
  <% end %>
  </div>

  <div class="form-group">
    <%= f.submit class: "btn btn-primary" %>
  </div>

<% end %>

您需要告诉您有关歌曲参数的强大参数：

def album_params
  params.require(:album).permit(:title, :image, :embed, :embed_html,
                                :songs_attributes => [:id, :_destroy, :title])
end

不要忘记包含您希望能够更新的所有歌曲属性。