Question

我尝试创建一个带有一系列检查的表单，以防止在同时创建三个模型记录期间出现重复：一个用于父级（假设它不存在），一个用于其子级（假设它不存在），并且一个用于子和用户之间的连接表（允许用户拥有自己的Song对象副本）。

在代码的当前状态下，检查看似通过，但是服务器日志显示ROLLBACK，并且不会保存任何内容到数据库除了父对象（艺术家）。
当我尝试使用对象的ID时，我收到错误undefined method id for nil:NilClass，或者＆＃34;找不到没有ID＆＃34;的对象。

以下代码在我的控制器中：

    class SongsController < ApplicationController
  before_action :authenticate_user!

  def create

    @artist = Artist.find_by(name: params[:artist][:name].strip.titleize) #look for the artist

    @song = Song.find_by(title: params[:artist][:songs_attributes]["0"][:title].strip.titleize)


    if @artist.present? && @song.present?
      @user_song = current_user.user_songs.find(@song_id)

      if @user_song.present?
        render html: "THIS SONG IS ALREADY IN YOUR PLAYLIST"
        render action: :new
      else
        @user_song = UserSong.create(user_id: current_user.id, song_id: @song.id)
        redirect_to root_path
      end

    elsif @artist.present? && !@song.present?

      @song = @artist.songs.build(title: params[:artist][:songs_attributes]["0"][:title].strip.titleize, lyrics: params[:artist][:songs_attributes]["0"][:lyrics].strip)

      @user_song = UserSong.create(user_id: current_user.id, song_id: @song.id)
      redirect_to root_path

    elsif !@artist.present?

      @artist = Artist.create(name: params[:artist][:name].strip.titleize)

      @song = @artist.songs.build(title: params[:artist][:songs_attributes]["0"][:title].strip.titleize, lyrics: params[:artist][:songs_attributes]["0"][:lyrics].strip)

      @user_song = UserSong.create(user_id: current_user.id, song_id: @song.id)
      redirect_to root_path
    else 
      render html: "SOMETHING WENT WRONG. CONTACT ME TO LET ME KNOW IF YOU SEE THIS MESSAGE"
    end
  end


  def index
    @songs = Song.all
  end

  def new
    @artist = Artist.new
    @artist.songs.build
    @user_song = UserSong.new(user_id: current_user.id, song_id: @song_id)
  end

  def show
    @song_id = params["song_id"]
    @song = Song.find(params[:id])
  end

  def destroy
    UserSong.where(:song_id => params[:id]).first.destroy
    flash[:success] = "The song has been from your playlist"
    redirect_to root_path
  end

  def edit
    @song = Song.find(params[:id])
    @artist = Artist.find(@song.artist_id)
  end

  def update
  end

  private
    def set_artist
      @artist = Artist.find(params[:id])
    end

    def artist_params
      params.require(:artist).permit(:name, songs_attributes: [:id, :title, :lyrics])
    end
    def set_song
      @song = Song.find(params["song_id"])
    end
end

模特：

class Artist < ApplicationRecord
  has_many :songs

  accepts_nested_attributes_for :songs, reject_if: proc { |attributes| attributes['lyrics'].blank? }
end

class Song < ApplicationRecord
  belongs_to :artist
  has_many :user_songs
  has_many :users, :through => :user_songs
end

class UserSong < ApplicationRecord
  belongs_to :song
  belongs_to :user
end

对不起，如果我没有足够的抽象。不确定如果没有错误消息，只是回滚（没有任何控制器中存在任何验证）。

Answer 1

感谢@coreyward和他指出胖模型瘦 - 控制器引理（从来不知道那是一件事），我能够切断代码并立即找到解决方案。在我的模型中，我使用了validates_uniqueness_of和scope来防止重复记录。在我的控制器中，我使用find_or_create_by来达成协议。

可能涉及的人，最终代码如下：

class SongsController < ApplicationController
  before_action :authenticate_user!

  def create
    @artist = Artist.find_or_create_by(name: params[:artist][:name].strip.titleize)
    @song = @artist.songs.find_or_create_by(title: params[:artist][:songs_attributes]["0"][:title].strip.titleize) do |song|
      song.lyrics = params[:artist][:songs_attributes]["0"][:lyrics].strip
    end
    @user_song = current_user.user_songs.find_or_create_by(song_id: @song.id) do |user_id|
      user_id.user_id = current_user.id
    end
    redirect_to root_path
  end



class Song < ApplicationRecord
  validates_uniqueness_of :title, scope: :artist_id

  belongs_to :artist
  has_many :user_songs
  has_many :users, :through => :user_songs
end

class Artist < ApplicationRecord

  validates_uniqueness_of :name
  has_many :songs

  accepts_nested_attributes_for :songs, reject_if: proc { |attributes| attributes['lyrics'].blank? }
end


class UserSong < ApplicationRecord
  validates_uniqueness_of :song_id, scope: :user_id

  belongs_to :song
  belongs_to :user
end

DB回滚创建操作

1 个答案: