没有宝石的分页Next，Previous，Name.order(:id).limit(10).offset(0)的按钮 [英] Paginate without a gem Next, Previous, buttons for Name.order(:id).limit(10).offset(0)

问题描述

一个多星期以来，我一直在寻找解决问题的方法.我的一项作业由于没有下一个/上一个功能而失去了10分，并且时间用完了.我仍然想弄清楚这一点.

I've been searching for a solution to my problem for over a week now. I have an assignment that I lost 10 pts on due to no next/prev functionality and ran out of time. I still want to figure this out though.

我用rails generate scaffold Ripple name:string message:text url:string创建了一个简短的单页站点，该站点显示了最近显示的10条帖子的索引(名称，消息，created_on，link_to"show").我仍然必须创建下一个，上一个，最新的，最旧的链接，以显示下10个，上一个10 ....的结果.我的代码.

I have Created a short single page site with rails generate scaffold Ripple name:string message:text url:string that shows an index of 10 most recent posts displays (name, message, created_on, link_to "show"). I still have to create a next, previous, newest, oldest links in view to show next 10, prev 10.... results. My code.

app\controllers\ripple_controller.rb

class RipplesController < ApplicationController  
  before_action :set_ripple, only: [:show, :update]  
  before_action :restrict_destroy_edit, only: [:edit, :destroy]   
  before_filter :set_page   
  helper_method :link_name_to_url, :next_button, :previous_button, :newest_button, :oldest_button, :is_next_page_available, :is_previous_page_available

  RIPPLES_PER_PAGE = 10

  def index   
    @ripples = Ripple.order(:id).limit(RIPPLES_PER_PAGE).offset(@page * RIPPLES_PER_PAGE) 
  end
  #All my show, new, destroy, edit, create ....

  def next_button

  end

  def previous_button

  end

  def newest_button

  end

  def oldest_button

  end

  def is_next_page_available?

  end

  def is_previous_page_available?

  end

  def set_page 
    @page = 5 
  end
private
...

\app\views\ripples.html.erb

<table>
  <thead>
    <tr>
      <th>Name</th>
      <th>Message</th>
      <th>Posted</th>
      <th>Show Ripple</th>
    </tr>
  </thead>

  <tbody>
    <% @ripples.each do |ripple| %>
      <tr>
        <td><%= link_name_to_url ripple %></td>
        <td><%= truncate(ripple.message, length: 50) %></td>
        <td><%= ripple.created_at.strftime("%B %d, %Y %l:%M %P") %></td>
        <td><%= button_to 'Show', ripple, :method => "get" %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<div id = "nav">
  <button><%= link_to 'Newest' %></button>
  <button><%= link_to 'Previous 10 Ripples' %></button>
  <button><%= link_to "Next 10 Ripples" %></button>
  <button><%= link_to 'Oldest' %></button>
  <button><%= link_to 'New Ripple', new_ripple_path, class: "button", method: :get %></button>
</div>

而且我尝试在Model中调用方法，但在下一个和上一个上一直出现undefined method "next" for #<Class:0xb4eabd0c>错误.

And I've tried calling methods in Model but keep getting undefined method "next" for #<Class:0xb4eabd0c> error on next and previous.

app\models\ripple.rb

class Ripple < ActiveRecord::Base
  default_scope -> {order(created_at: :desc)}
  validates :name, :message, presence: true
  validates :url, allow_blank: true, format: {
  with: URI::regexp(%w(http https)),
      message: "Must be a url starting with http:// or https://"
  }

  def next
    Ripple.order(:id).limit(10).offset((@page - 1) * 10)
  end

  def previous
    Ripple.order(:id).limit(10).offset((@page + 1) * 10)
  end
end

如何使用order().limit().offset实现下一个和上一个，也许使用@page来跟踪我在ActiveRecord中的位置.也许像

How would I implement next and previous using the order().limit().offset and maybe use @page to keep track of where I'm at in the ActiveRecord. Maybe something like

def next_button
  @page -= 1
end

我可以用两种方式调用索引"<%= link_to Next 10" next_button %>:

that I can call in index "<%= link_to Next 10" next_button %> either way I'm out of ideas that might work.

感谢您的帮助.

推荐答案

这里有几件事.首先，控制器方法应与匹配路线一起使用.这是一个请求周期，您单击应用程序上的按钮，向服务器发出请求，然后向服务器发出信息.

A few things here. Firstly, controller methods should be used with matching routes. It's a request cycle where you click a button on your app, it makes a request to your server, then your server response with information.

以这种方式将其作为helper_method放置时，您的next_button方法将不起作用.为了使您的控制器正常工作，您应该具有与您的控制器方法匹配的路由.在命令行中执行rake routes.您需要在route.rb文件

Your next_button method is not going to work when you put it as a helper_method this way. In order to make your controller work, you should have routes that match to your controller method. Do a rake routes in your command line. You need to see something like this in your route.rb file

get 'ripple/next', 'ripple#next'

有关routes的更多信息: http://guides.rubyonrails. org/routing.html#controller-namespaces-and-routing

在您的控制器中，您可以拥有

And in your controller, you could have

def next
  page = params[:page]
  params[:page] += 1
  @ripples = Ripple.find_ripples_on_page(page, PAGE_SIZE)
  render :index
end

然后在erb视图中，您应该访问"此特定路由，而不是调用该方法.

Then in your erb view, your should be 'visiting' this particular route, not calling the method.

第二，您不能依赖模型中的类实例变量.相反，您应该将其放在会话中或作为查询字符串的一部分.正如上面的控制器代码一样，我将其放在会话中，这是一个本地存储.有关session的更多信息: http://guides.rubyonrails.org/action_controller_overview.html#session

Secondly, you can not rely on class instance variable in your model. Instead, you should put it in your session or as part of a query string. As above controller code, I put it in session, which is a local storage. More about session: http://guides.rubyonrails.org/action_controller_overview.html#session

最后，您的模型.

def find_ripples_on_page(page, PAGE_SIZE)
  Ripple.where( ... ) # you can figure this out, depending on if you want to rank by updated_at or other filter
end

旁注:控制器中的helper_method用于检索未向控制器发出命令的信息.该宏所做的全部工作就是使用class_eval并将控制器中的方法复制"到renderer.

Side note: helper_method in controller is for retrieving information not giving command to the controller. All this macro does is use class_eval and 'copy' the method you have in controller into the renderer.

如果可以使用宝石，请使用will_paginate.

If you can use a gem, use will_paginate.

http://guides.rubyonrails.org/routing.html#控制器命名空间和路由

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