未定义的方法`strftime'

Question

HY  在我创建了用户的事件后，我试着看到它，但是我收到了一个错误   错误未定义方法`strftime'代表nil：NilClass

我不明白为什么我会收到此错误，因为在应用关联之前一切正常

show.html.erb

     <p class="info">Evénement crée le <%= @calendar.published_on.strftime("%e %B, %Y") %>
   10 <%= simple_format @calendar.description %>
   11 
   12 <p>edit_calendar_path(:id)</p>
   13 <%= link_to 'Edit', edit_calendar_path(@calendar) %> |
   14 <%= link_to 'Back', user_calendars_path %> |

calendar.controler.rb

  def index
    #@content_calendars = @user.Calendar
  @user = current_user
    @content_calendars = @user.Calendar.all
    @content_calendars_by_dates = @content_calendars.group_by(&:published_on)
    @date = params[:date] ? Date.parse(params[:date]) : Date.today
  end

  def show
    @user = current_user
   # @calendar = @user.find_all_calendar_by()
    #  @tasks = @project.tasks.find_all_by_complete(false)
    @calendar = @user.calendar.find(params[:id])
  end


  def new
    @user = current_user
   # @calendar = @user.build_calendar
   @calendar = @user.calendar.build
  end

def create
    @user = current_user
    @calendar = @user.calendar.build(params[:id])
    #@calendar = @user.Calendar.new(params[:calendar])
    if @calendar.save
       #redirect_to calendar_path(@user)
       redirect_to [@user,@calendar]
       #, notice: "L evenement a ete cree"
    else
      render :new
    end
  end

show.html.erb

<% if user_signed_in? %>
     <%= stylesheet_link_tag "index.css" %>
     <%= stylesheet_link_tag "calendar.css" %>

    <%= csrf_meta_tags %>

      <div id="white-container"> <!-- Start White Container -->
         <br/>
         <div class="page-width"><!-- Start Page Width Content Box -->
      <div class="contentbox">
        <div id="calendar">New calendar</div><br />

         <%= render 'form' %>
         <%= link_to 'Back', user_calendars_path %>

    <% else %>
        <span>
          <% flash[:info] = ''%>
        </span>
            <%= render 'devise/sessions/form' %>
    <% end %>

        </div>
      </div>
    </div>

_form.html.erb

<%= form_for([@user, @calendar]) do |f| %>
  <% if @calendar.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@calendar.errors.count, "error") %> prohibited this calendar from being saved:</h2>

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

  <div class="field">
    <%= f.label :event %><br />
    <%= f.text_field :event %>
  </div>
  <div class="field">
    <%= f.label :published_on %><br />
    <%= f.text_field :published_on, :size=>"10", :text_align=>"center" %>
  </div>
  <div class="field">
    <%= f.label :description %><br />
    <%= f.text_area :description, :rows => "10", :cols=> "30" %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>