ruby-on-rails - 未定义的方法 `length' 为 nil :NilClass

Question

当我创建一个新用户并查看用户的个人资料时，我收到以下错误，我认为是因为用户尚未创建状态:

undefined method `length' for nil:NilClass

它来自 Status_form:

<%= form_for [@status], :url => user_status_path(current_user) do |f| %>
  <div class="field">
    <%= f.text_area :content, id:"status_box", maxlength:350, placeholder: "Say something." %>
  </div>
  <%= f.submit "Update", id:"status_btn", class: "btn btn-small btn-primary" %>

  <span id="counter">Characters left: <%= 350 - @status.content.length %></span> #this is the source of the error

  <script type="text/javascript">
    $('#status_box').keyup(function () {
        var left = 350 - $(this).val().length;
        if (left < 0) {
            left = 0;
        }
        $('#counter').text('Characters left: ' + left);
    });
  </script>
<% end %>

用户 Controller :

def new
  @user = User.new
end

def create
  @user = User.new(params[:user])
  if @user.save
    sign_in @user
    redirect_to root_path
  else
    render 'new'
  end
end

def show
  @user = User.find(params[:id])
  @status = @user.status || @user.build_status
end

Answer 1

这是因为您有默认值 nil为 content列。所以你不能打电话length在 nil .如果您想使用 length在 content您需要设置 default值为 empty string("")或者您可以使用 to_s先然后length

   <%= 350 - @status.content.to_s.length %>

或

   <%= 350 - (@status.content.try(:length) || 0) %>