ruby-on-rails - 如何解决nil :NilClass errror in Rails 4?

Question

我目前在创建帖子时遇到问题，我似乎总是得到未定义的方法“用户名”或“电子邮件”，但是当使用 current_user.username 或 current_user.email 时它会显示得很好......

论坛线程 Controller

class ForumThreadsController < ApplicationController
before_action :authenticate_user!, except: [:index, :show]
before_action :set_forum_thread, except: [:index, :new, :create]

def index
@q = ForumThread.search(params[:q])
@forum_threads = @q.result(distinct: true)
@forum_threads = ForumThread.paginate(:page => params[:page], :per_page => 3)
end

def show
@forum_posts = ForumThread.find(params[:id])
@forum_post.user = current_user
@forum_post = ForumPost.new
@forum_posts = ForumPost.paginate(:page => params[:page], :per_page => 3)
end

def new
@forum_thread = ForumThread.new
@forum_thread.forum_posts.new
end

def create
@forum_thread = current_user.forum_threads.new forum_thread_params
@forum_thread.forum_posts.first.user_id = current_user.id

if @forum_thread.save
  redirect_to @forum_thread
else
  render action: :new
end
end

def edit
end

def update
if @forum_thread.update forum_thread_params
redirect_to @forum_thread
else
render 'edit'
end
end

def destroy
@forum_thread.destroy
redirect_to root_path
end

private

def set_forum_thread
  @forum_thread = ForumThread.find(params[:id])
end

论坛帖子 Controller

class ForumThreads::ForumPostsController < ApplicationController
  before_action :authenticate_user!, except: [:index, :show]
  before_action :set_forum_thread

  def new
    @forum_post = @forum_thread.forum_posts.new forum_post_params
    @forum_post.user = current_user
  end


  def create
    @forum_post = @forum_thread.forum_posts.new forum_post_params
    @forum_post.user = current_user
    if @forum_post.save
      redirect_to forum_thread_path(@forum_thread, anchor: "forum_post_#{@forum_post.id}"), notice: "Successfully posted!"
    else
      redirect_to @forum_thread, alert: "Unable to save your post"
    end
  end

  def edit
  end

  def update
     if @forum_post.update(forum_post_params)
        redirect_to @forum_thread
     else
        render 'edit'
     end
  end


  private

    def set_forum_thread
      @forum_thread = ForumThread.find(params[:forum_thread_id])
    end

    def forum_post_params
      params.require(:forum_post).permit(:body)
    end
end

日志

I, [2015-11-18T06:16:17.418239 #16523]  INFO -- : Started GET "/forum/forum_threads/17" for 24.220.125.144 at 2015-11-18 06:16:17 -0600
I, [2015-11-18T06:16:17.453154 #16523]  INFO -- : Processing by ForumThreadsController#show as HTML
I, [2015-11-18T06:16:17.453292 #16523]  INFO -- :   Parameters: {"id"=>"17"}
D, [2015-11-18T06:16:17.479120 #16523] DEBUG -- :   ^[[1m^[[36mForumThread Load (0.5ms)^[[0m  ^[[1mSELECT  `forum_threads`.* FROM `forum_threads` WHERE `forum_threads`.`id` = $
D, [2015-11-18T06:16:17.487690 #16523] DEBUG -- :   ^[[1m^[[35mCACHE (0.0ms)^[[0m  SELECT  `forum_threads`.* FROM `forum_threads` WHERE `forum_threads`.`id` = 17 LIMIT 1  [["i$
D, [2015-11-18T06:16:17.503484 #16523] DEBUG -- :   ^[[1m^[[36mUser Load (0.9ms)^[[0m  ^[[1mSELECT  `users`.* FROM `users` WHERE `users`.`deleted_at` IS NULL AND `users`.`id` $
D, [2015-11-18T06:16:17.541778 #16523] DEBUG -- :   ^[[1m^[[35mUser Load (0.5ms)^[[0m  SELECT  `users`.* FROM `users` WHERE `users`.`deleted_at` IS NULL AND `users`.`id` = 9 L$
D, [2015-11-18T06:16:17.573968 #16523] DEBUG -- :   ^[[1m^[[36mForumPost Load (0.6ms)^[[0m  ^[[1mSELECT `forum_posts`.* FROM `forum_posts` WHERE `forum_posts`.`forum_thread_id$
D, [2015-11-18T06:16:17.579587 #16523] DEBUG -- :   ^[[1m^[[35mCACHE (0.0ms)^[[0m  SELECT  `users`.* FROM `users` WHERE `users`.`deleted_at` IS NULL AND `users`.`id` = 9 LIMIT$
I, [2015-11-18T06:16:17.583134 #16523]  INFO -- :   Rendered forum_posts/_forum_post.html.erb (7.0ms)
I, [2015-11-18T06:16:17.583329 #16523]  INFO -- :   Rendered forum_threads/show.html.erb within layouts/application (48.1ms)
I, [2015-11-18T06:16:17.583711 #16523]  INFO -- : Completed 500 Internal Server Error in 130ms (ActiveRecord: 6.8ms)
F, [2015-11-18T06:16:17.585545 #16523] FATAL -- :
ActionView::Template::Error (undefined method `email' for nil:NilClass):
    1: <%= div_for forum_post do %>
    2: <div class="pull-avatar-left" style="padding-right: 20px; padding-bottom: 10px;"><%= image_tag current_user.gravatar_url(:size => 65), :class => "img-circle avatar" %><$
    3: <div class="forum-post-container" style="margin-top: 20px; margin-left: 20px; padding-bottom: 10px;">
    4: <p class="text-muted">Posted by <%= forum_post.user.email %> <%= local_time_ago forum_post.created_at %></p>
    5:   <p><%= forum_post.body %></p>
    6: </div>
    7: <% end %>
  app/views/forum_posts/_forum_post.html.erb:4:in `block in _app_views_forum_posts__forum_post_html_erb___2875746267982681747_45837340'
  app/views/forum_posts/_forum_post.html.erb:1:in `_app_views_forum_posts__forum_post_html_erb___2875746267982681747_45837340'
  app/views/forum_threads/show.html.erb:6:in `_app_views_forum_threads_show_html_erb__3506623455216328957_43396520'

Answer 1

将部分 _forum_post 中的代码更改为:

<%= div_for @forum_post do %>

并在您的部分 .它将无任何错误地工作。