ruby-on-rails - ruby 在 rails 上。通过 View 更改 Controller 的变量并渲​​染更新的 View

Question

我在 RoR 甚至网络编程方面都是初学者。所以我想我的问题对于很多开发者来说都很简单!

我正在实现简单的周日历，它应该有日期的名称和两个“按钮”-“下周”和“上一周”。这就是开始!

我有带有索引操作的 Controller :

    def index

      @today = Date::today
      @monday = @today.beginning_of_week
      @sunday = @today.end_of_week

      @currentweek = @monday..@sunday    
   end

以及另外两个操作:

  def go_next_week
      @monday = @sunday + 1
      @sunday = @monday.end_of_week
  end

  def go_prev_week
      @sunday = @monday - 1
      @monday = @sunday.beginning_of_week
  end

索引 View 代码:

<div class="wrapper">
  <table class="data">
    <thead>
    <tr class="month-names">      
      <td><%= form_tag(work_days_go_prev_week_path, method: "get") do %>
            <%= submit_tag(l(("workdays_show_prev" + period).to_sym)) %>
        <% end %>
      </td>
      <td><%= render :partial => 'days_names_header' %></td>
      <td><%= form_tag(work_days_go_next_week_path, method: "get") do %>
            <%= submit_tag(l(("workdays_show_next" + period).to_sym)) %>
        <% end %>
      </td>
    </tr>
    </thead>
  </table>
</div>

以及路线文件:

RedmineApp::Application.routes.draw do
  match 'work_days/go_next_week'            ,:to => 'work_days#go_next_week',           via: [:get]
  match 'work_days/go_prev_week'            ,:to => 'work_days#go_prev_week',           via: [:get]
  match 'work_days/(:action(/:id))',via: [:get], :controller => 'work_days'
end

短期内该阶段的主要目标是:

• Controller 有一个日期变量“星期一”、“星期日”和范围 “当前周”

• 索引 View 根据变量显示天数表

• 索引 View 有 2 个“按钮”:“下周”和“上周”

• 单击此按钮应更改 Controller 的变量

• 索引 View 应使用更改后的 Controller 变量“刷新”

该代码不起作用。单击“上个月”按钮时，我在日志中收到此类错误:

Started GET "/work_days/go_prev_week?tf8=%E2%9C%93&commit=Previous+week" for 127.0.0.1 at 2015-12-09 14:00:27 +0600 Processing by WorkDaysController#go_prev_week as HTML Parameters: {"utf8"=>"✓","commit"=>"Previous week"} Current user: admin (id=1) Completed 500 Internal Server Error in 3ms (ActiveRecord: 0.2ms)

NoMethodError (undefined method `-' for nil:NilClass)

Answer 1

I'm very beginner in RoR and even in web-programming.

欢迎!

---

您的问题是您正在使用相互依赖的 @instance_variables 填充 Controller 操作:

def go_next_week
  @monday = @sunday + 1           # needs @sunday
  @sunday = @monday.end_of_week   # needs @monday
end

在老式编程中，这可能会导致无法识别的引用错误或堆栈溢出错误，通常是由于无限 recursion .

错误证实了这一点:

undefined method `-' for nil:NilClass

Ruby 与大多数其他语言不同，它将未声明的变量分配给 NilClass 对象。这使得开发人员很难确定错误 - 基本上，如果您收到 NilClass 的未定义方法，则表明您尚未声明变量。

--

解决方法是将您尝试操作的数据获取到类的实例中。这可以通过 before_action 来实现过滤器:

#app/controllers/work_days_controller.rb
class WorkDaysController < ApplicationController
   before_action :set_dates

   def index
      #@today, @monday, @sunday will be available in here.
   end

   private

   def set_dates
      @today = Date::today
      @monday = @today.beginning_of_week
      @sunday = @today.end_of_week
   end
end 

---

您还可以改进您的路线以利用 resources指令:

#config/routes.rb
resources :work_days do
   get :go_next_week, on: :collection
   get :go_prev_week, on: :collection
end