用于nil的Ruby未定义方法`strftime':NilClass

Question

我只是在短时间内与Ruby合作,今天我在日历上处理请求时遇到了问题.我花时间在stackoverflow,ruby指南等上搜索不同的未定义方法错误文档,以及查看strftime.我找到了一个解决方案,使用try部分解决了我的问题,但现在它实际上并没有通过strftime来显示请求,即使rails服务器正在帖子中提取它.我可以很好地使用我的日历,然后点击新的请求按钮,填写表单,但是当我发布该表单时,浏览器会给我这样的信息:

undefined method `strftime' for nil:NilClass

Extracted source (around line #3):

1: <h1><%= @vacationrequest.request_name %></h1>
2: 
3: <p class="info">Requested For <%= @vacationrequest.request_date.strftime("%B %e, %Y") %></p>
4: 
5: <%= simple_format @vacationrequest.message %>
6: 

我在Rails服务器上收到此错误:

Started GET "/vacationrequests/1" for 127.0.0.1 at 2012-10-17 15:18:14 -0400
Processing by VacationrequestsController#show as HTML
Parameters: {"id"=>"1"}
?[1m?[35mVacationrequest Load (0.0ms)?[0m SELECT "vacationrequests".* FROM "v
acationrequests" WHERE "vacationrequests"."id" = ? LIMIT 1 [["id", "1"]]
Rendered vacationrequests/show.html.erb within layouts/application (15.6ms)
Completed 500 Internal Server Error in 31ms

ActionView::Template::Error (undefined method strftime' for nil:NilClass):
1: <h1><%= @vacationrequest.request_date %></h1>
2:
3: <p class="info">Requested For <%= @vacationrequest.request_date.strftime(
"%B %e, %Y") %></p>
4:
5: <%= simple_format @vacationrequest.message %>
6:
app/views/vacationrequests/show.html.erb:3:inapp_views_vacationrequests_sho
w_html_erb_217743956_18446544'

这是我的展示视图:

<h1><%= @vacationrequest.request_name %></h1>

<p class="info">Requested For <%= @vacationrequest.request_date.strftime("%B %e, %Y") %></p>

<%= simple_format @vacationrequest.message %>

<p>
  <%= link_to "Edit Request", edit_vacationrequest_path(@vacationrequest) %> |
  <%= link_to "Back to Requests", vacationrequests_path %>
</p>

这是用户将请求信息放入的_form:

<%= form_for @vacationrequest do |f| %>
  <% if @vacationrequest.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@vacationrequest.errors.count, "error") %> prohibited this request from being saved: if this continue to happens please email the error to alex@allsafeindustries.com</h2>
      <ul>
      <% @vacationrequest.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :request_name %><br />
    <%= f.text_field :request_name %>
  </div>
  <div class="field">
    <%= f.label :request_date %><br />
    <%= f.text_field :request_date %>
  </div>
  <div class="field">
    <%= f.label :message %><br />
    <%= f.text_area :message %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

最后这是我的控制器中的show和index方法:

  def index
    @vacationrequests = Vacationrequest.all
    @vacationrequests_by_date = @vacationrequests.group_by(&:request_date)
    @date = params[:date] ? Date.parse(params[:date]) : Date.today
  end

  def show
    @vacationrequest = Vacationrequest.find(params[:id])
  end

任何人都可以指引我到不合适的地方或为什么这是零？谢谢.

回答这里的答案是我现在从服务器获得的:

Started POST "/vacationrequests" for 127.0.0.1 at 2012-10-17 20:18:00 -0400
Processing by VacationrequestsController#create as HTML
  Parameters: {"utf8"=>"?", "authenticity_token"=>"E1+xXP0pAIQpwMZruswxIZIrTZB3b
c3NlW3iRv9OLqU=", "vacationrequest"=>{"request_name"=>"One more time", "request_
date"=>"10/31/2012", "message"=>"Lucky number 7?"}, "commit"=>"Create Vacationre
quest"}
  ?[1m?[35m (0.0ms)?[0m  begin transaction
  ?[1m?[36mSQL (15.6ms)?[0m  ?[1mINSERT INTO "vacationrequests" ("created_at", "
message", "request_date", "request_name", "updated_at") VALUES (?, ?, ?, ?, ?)?[
0m  [["created_at", Thu, 18 Oct 2012 00:18:00 UTC +00:00], ["message", "Lucky nu
mber 7?"], ["request_date", nil], ["request_name", "One more time"], ["updated_a
t", Thu, 18 Oct 2012 00:18:00 UTC +00:00]]
  ?[1m?[35m (109.2ms)?[0m  commit transaction
Redirected to http://localhost:3000/vacationrequests/7
Completed 302 Found in 125ms (ActiveRecord: 124.8ms)


Started GET "/vacationrequests/7" for 127.0.0.1 at 2012-10-17 20:18:01 -0400
Processing by VacationrequestsController#show as HTML
  Parameters: {"id"=>"7"}
  ?[1m?[36mVacationrequest Load (0.0ms)?[0m  ?[1mSELECT "vacationrequests".* FRO
M "vacationrequests" WHERE "vacationrequests"."id" = ? LIMIT 1?[0m  [["id", "7"]
]
  Rendered vacationrequests/show.html.erb within layouts/application (15.6ms)
    Completed 500 Internal Server Error in 16ms

ActionView::Template::Error (undefined method `strftime' for nil:NilClass):
    1: <h1><%= @vacationrequest.request_name %></h1>
    2: <%= debug @vacationrequest %>
    3: <p class="info">Requested For <%= @vacationrequest.request_date.strftime(
"%B %e, %Y") %></p>
    4:
    5: <%= simple_format @vacationrequest.message %>
    6:
  app/views/vacationrequests/show.html.erb:3:in `_app_views_vacationrequests_sho
w_html_erb___377763931_36688344'

我还使用了视图调试并检查了我的方案,所有属性似乎都正确排列.

至于评论中的请求是我的Vacationrequest模型:

class Vacationrequest < ActiveRecord::Base
  attr_accessible :message, :request_name, :request_date
end

我再一次感谢你的帮助.

这是架构:

ActiveRecord::Schema.define(:version => 20121016194123) do

  create_table "vacationrequests", :force => true do |t|
    t.string   "request_name"
    t.date     "request_date"
    t.text     "message"
    t.datetime "created_at",   :null => false
    t.datetime "updated_at",   :null => false
  end
end

和创建控制器动作代码:

def create
  @vacationrequest = Vacationrequest.new(params[:vacationrequest])
  if @vacationrequest.save
    redirect_to @vacationrequest, notice: "Created Request!"
  else
    render :new
  end
end

正如我正在看这个,问题的一部分我的架构是复数而我的控制器是单数的？再次感谢.

Answer 1

首先,您必须确保在通过应用ActiveRecord验证创建记录之前是否填充了'request_date'.

其次,您可以使用ruby的try方法来避免此类异常

<%= @vacationrequest.try(:request_date).try(:strftime, '%B %e, %Y') %>

快乐的编码!

更新

在较新版本的Ruby中,您可以使用&.- > lonely operator而不是上面的解决方案.

<%= @vacationrequest&.request_date&.strftime('%B %e, %Y') %>

Answer 2

Shioyama 非常感谢您的建议：

验证 :request_date, :presence => true

我真的会投入时间来学习 Rails 所提倡的调试和验证。因此，我特别发现 JQuery 中的日期选择器没有正确传递。我进入我的assests > javascripts > Vacationrequests.js.coffee，发现我在最后留下了 () ，如下所示：

jQuery ->
  $('#vacationrequest_request_date').datepicker()
    dateFormat: 'yy-mm-dd'

一旦我像这样删除括号：

jQuery ->
  $('#vacationrequest_request_date').datepicker
    dateFormat: 'yy-mm-dd'

一切正常，索引、显示、编辑、更新、新建。谢谢你们的所有建议，并向我展示了如何解决这个问题。