我是否正在创建一个未定义的 nil 方法

Question

除了我想检查帖子是否属于user_id时，一切都正常工作。

我基本上要实现的是隐藏删除帖子按钮，以便其他用户无法删除它。

当我做我的第一个项目时，我仍然对 Ruby on rails 很陌生，我添加了一个 if 语句来检查它是否属于 user_id。现在我正在尝试做同样的事情，但我不断收到NoMethodError

个人资料代码：

<div class="container">
    <div class="row">
        <% if user_signed_in? %>
            <% if @post.user_id == current_user.id %>
                <div class="col-md-5">
                    <%= render '/components/post_form' %>
                </div>
            <%end%>
        <%end%>
    </div>
</div>

后控制器：

class PostsController < ApplicationController
    before_action :find_post, only: [:show, :edit, :update, :destroy]
    #new post
    def new
        @post = Post.new
    end
    #create post
    def create
        @post = Post.new(posts_params)
        @post.user_id = current_user.id
        respond_to do |f|
            if (@post.save)
                f.html {redirect_to :back}
            else
                f.html {redirect_to :back, notice: "An error happened while submitting your post. Please try again."}
            end         
        end
    end
    #show post 
    def show
        if (User.find_by_username(params[:id]))
            @post = params[:id]
        end
    end
    #destroy post
    def destroy
        @post = Post.find(params[:id])
        @post.destroy
        redirect_to :back
    end
    #private
    private
        def posts_params
            params.require(:post).permit(:user_id, :content)
        end
        def find_post
            @post = Post.find(params[:id])          
        end
end

页面控制器：

class PagesController < ApplicationController
  def index
  end
  def home
    @posts = Post.all
  end
  def profile
    if (User.find_by_username(params[:id]))
        @username = params[:id]
    else
        redirect_to root_path, :notice => "user not found"
    end
    @posts = Post.all.where( "user_id = ?", User.find_by_username(params[:id]) )
    @newPost = Post.new
  end
  def explore
    @posts = Post.all
  end
end

发布架构：

  create_table "posts", force: true do |t|
    t.text     "content"
    t.integer  "user_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

更新

我得到的错误：

NoMethodError in Pages#profile

完整跟踪：

app/views/pages/profile.html.erb:4:in `_app_views_pages_profile_html_erb___203732305_53267256'
actionview (4.1.8) lib/action_view/template.rb:145:in `block in render'
activesupport (4.1.8) lib/active_support/notifications.rb:161:in `instrument'
actionview (4.1.8) lib/action_view/template.rb:339:in `instrument'
actionview (4.1.8) lib/action_view/template.rb:143:in `render'
actionview (4.1.8) lib/action_view/renderer/template_renderer.rb:55:in `block (2 levels) in render_template'
actionview (4.1.8) lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
activesupport (4.1.8) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.1.8) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.1.8) lib/active_support/notifications.rb:159:in `instrument'
actionview (4.1.8) lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
actionview (4.1.8) lib/action_view/renderer/template_renderer.rb:54:in `block in render_template'
actionview (4.1.8) lib/action_view/renderer/template_renderer.rb:62:in `render_with_layout'
actionview (4.1.8) lib/action_view/renderer/template_renderer.rb:53:in `render_template'
actionview (4.1.8) lib/action_view/renderer/template_renderer.rb:17:in `render'
actionview (4.1.8) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionview (4.1.8) lib/action_view/renderer/renderer.rb:23:in `render'
actionview (4.1.8) lib/action_view/rendering.rb:99:in `_render_template'
actionpack (4.1.8) lib/action_controller/metal/streaming.rb:217:in `_render_template'
actionview (4.1.8) lib/action_view/rendering.rb:82:in `render_to_body'
actionpack (4.1.8) lib/action_controller/metal/rendering.rb:32:in `render_to_body'
actionpack (4.1.8) lib/action_controller/metal/renderers.rb:32:in `render_to_body'
actionpack (4.1.8) lib/abstract_controller/rendering.rb:25:in `render'
actionpack (4.1.8) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (4.1.8) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
activesupport (4.1.8) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
activesupport (4.1.8) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (4.1.8) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
actionpack (4.1.8) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
activerecord (4.1.8) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
actionpack (4.1.8) lib/action_controller/metal/instrumentation.rb:40:in `render'
actionpack (4.1.8) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (4.1.8) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (4.1.8) lib/abstract_controller/base.rb:189:in `process_action'
actionpack (4.1.8) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (4.1.8) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
activesupport (4.1.8) lib/active_support/callbacks.rb:113:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:113:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:149:in `block in halting_and_conditional'
activesupport (4.1.8) lib/active_support/callbacks.rb:229:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:229:in `block in halting'
activesupport (4.1.8) lib/active_support/callbacks.rb:229:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:229:in `block in halting'
activesupport (4.1.8) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.8) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.8) lib/active_support/callbacks.rb:166:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:166:in `block in halting'
activesupport (4.1.8) lib/active_support/callbacks.rb:86:in `call'
activesupport (4.1.8) lib/active_support/callbacks.rb:86:in `run_callbacks'
actionpack (4.1.8) lib/abstract_controller/callbacks.rb:19:in `process_action'
actionpack (4.1.8) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (4.1.8) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (4.1.8) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.1.8) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.1.8) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.1.8) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (4.1.8) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
activerecord (4.1.8) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (4.1.8) lib/abstract_controller/base.rb:136:in `process'
actionview (4.1.8) lib/action_view/rendering.rb:30:in `process'
actionpack (4.1.8) lib/action_controller/metal.rb:196:in `dispatch'
actionpack (4.1.8) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.1.8) lib/action_controller/metal.rb:232:in `block in action'
actionpack (4.1.8) lib/action_dispatch/routing/route_set.rb:82:in `call'
actionpack (4.1.8) lib/action_dispatch/routing/route_set.rb:82:in `dispatch'
actionpack (4.1.8) lib/action_dispatch/routing/route_set.rb:50:in `call'
actionpack (4.1.8) lib/action_dispatch/journey/router.rb:73:in `block in call'
actionpack (4.1.8) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.1.8) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.1.8) lib/action_dispatch/routing/route_set.rb:678:in `call'
warden (1.2.6) lib/warden/manager.rb:35:in `block in call'
warden (1.2.6) lib/warden/manager.rb:34:in `catch'
warden (1.2.6) lib/warden/manager.rb:34:in `call'
rack (1.5.5) lib/rack/etag.rb:23:in `call'
rack (1.5.5) lib/rack/conditionalget.rb:25:in `call'
rack (1.5.5) lib/rack/head.rb:11:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/flash.rb:254:in `call'
rack (1.5.5) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.5.5) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/cookies.rb:560:in `call'
activerecord (4.1.8) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.1.8) lib/active_record/connection_adapters/abstract/connection_pool.rb:621:in `call'
activerecord (4.1.8) lib/active_record/migration.rb:380:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.1.8) lib/active_support/callbacks.rb:82:in `run_callbacks'
actionpack (4.1.8) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.1.8) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.1.8) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.1.8) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.1.8) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.1.8) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.1.8) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.5) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.5) lib/rack/runtime.rb:17:in `call'
activesupport (4.1.8) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
rack (1.5.5) lib/rack/lock.rb:17:in `call'
actionpack (4.1.8) lib/action_dispatch/middleware/static.rb:84:in `call'
rack (1.5.5) lib/rack/sendfile.rb:112:in `call'
railties (4.1.8) lib/rails/engine.rb:514:in `call'
railties (4.1.8) lib/rails/application.rb:144:in `call'
rack (1.5.5) lib/rack/lock.rb:17:in `call'
rack (1.5.5) lib/rack/content_length.rb:14:in `call'
rack (1.5.5) lib/rack/handler/webrick.rb:60:in `service'
C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

更新

部分形式：

<%= simple_form_for @newPost do |f| %>
  <%= f.label :content %>
  <%= f.text_field :content, autofocus: true %>
  <%= f.button :submit %>
<% end %>

Answer 1

替换它：

<div class="container">
    <div class="row">
        <% if user_signed_in? %>
            <% if @post.user_id == current_user.id %>
                <div class="col-md-5">
                    <%= render '/components/post_form' %>
                </div>
            <%end%>
        <%end%>
    </div>
</div>

有了这个：

<div class="container">
   <% if user_signed_in? && @newPost.present? && @newPost.user_id == current_user.id %>
    <div class="row">
      <div class="col-md-5">
         <%= render '/components/post_form' %>
      </div>
    </div>
 <%end%>
</div>

请注意，您在控制器中定义了@newPost，但您的视图正在尝试使用不存在的@post。

此外，您可能希望将@newPost传递到部分，如下所示：

<%= render '/components/post_form', object: @newPost %>