基於Ruby on Rails的論壇實現（新手指南）

用Rails實現一個簡單的論壇系統，大致的架構爲：站點擁有多個Forum，每個Forum有多個Topic，而每個Topic又有多個Reply。原文鏈接：[url]http://railsonedge.blogspot.com/2008/02/rails-forum-tutorial-for-beginners-part.html[/url]。

我下載的是目前最新的Rails版本2.1，數據庫使用的是Sql Server 2000，應用程序所在目錄爲F:\Ruby\railsdoc\myforum。首先快速地依照以下步驟創建Forum類：

[list=1][*]執行[color=red]rails myforum[/color]生成完整的目錄結構；
[*]執行[color=red]ruby script/generate scaffold Forum name:string description:text[/color]創建相關的數據庫移植文件及model、controller、views文件；
[*]修改database.yml文件中的相關數據庫配置信息；
[*]在Sql Server中新建名爲myforum的數據庫，並執行[color=red]rake db:migrate[/color]創建forums表；
[*]修改environment.rb文件使頁面能正常顯示中文。[/list]
這樣Forum頁面就完成了，啓動服務器後在瀏覽器鍵入http://127.0.0.1:3000/forums便能進行CRUD操作了。

刪除/public/index.html，修改/config/routes.rb，使得http://localhost:3000直接指向Forum列表：
[quote]map.root :controller => 'forums', :action => 'index'[/quote]

分別執行以下命令創建Topic和Reply的相關文件及數據庫表：
[quote]ruby script/generate scaffold Topic forum:references user:references subject:string body:text

ruby script/generate scaffold Reply topic:references user:references subject:string body:text

rake db:migrate[/quote]

表Forum
[img]/upload/attachment/43459/16483034-0716-32ef-962a-0a966ac167bd.jpg[/img]

表Topic
[img]/upload/attachment/43461/0914d1eb-130c-3588-a162-2390068d7c60.jpg[/img]

表Reply
[img]/upload/attachment/43463/e220aa77-6bfe-376f-a043-04094f002db9.jpg[/img]

修改/config/routes.rb

……
map.resources :forums, :has_many => :topics  # Add
map.resources :topics, :has_many => :replies  # Add
map.resources :replies
…… 

修改/app/models/forum.rb

class Forum < ActiveRecord::Base
  has_many :topics  # Add
  has_many :replies, :through => :topics  # Add
end

修改/app/models/topic.rb

class Topic < ActiveRecord::Base
  belongs_to :forum  # Add
  belongs_to :user  # Add
  has_many :replies  # Add
end

修改/app/models/reply.rb

class Reply < ActiveRecord::Base
  belongs_to :topic  # Add
  belongs_to :user  # Add
end

修改/app/controllers/topics_controller.rb

class TopicsController < ApplicationController
  before_filter :load_forum  # Add

  def load_forum  # Add
    @forum = Forum.find(params[:forum_id])  # Add
  end  # Add

  # GET /topics
  # GET /topics.xml
  def index
   @topics = @forum.topics  # Edit: @topics = Topic.find(:all)

    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @topics }
    end
  end

  # GET /topics/1
  # GET /topics/1.xml
  def show
   @topic = @forum.topics.find(params[:id])  # Edit: @topic = Topic.find(params[:id])

    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @topic }
    end
  end

  # GET /topics/new
  # GET /topics/new.xml
  def new
   @topic = @forum.topics.build  # Edit: @topic = Topic.new

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @topic }
    end
  end

  # GET /topics/1/edit
  def edit
   @topic = @forum.topics.find(params[:id])  # Edit: @topic = Topic.find(params[:id])
  end

  # POST /topics
  # POST /topics.xml
  def create
   @topic = @forum.topics.build(params[:topic])  # Edit: @topic = Topic.new(params[:topic])

    respond_to do |format|
      if @topic.save
        flash[:notice] = 'Topic was successfully created.'
       format.html { redirect_to(@forum) }  # Edit: format.html { redirect_to(@topic) }
        format.xml  { render :xml => @topic, :status => :created, :location => @topic }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @topic.errors, :status => :unprocessable_entity }
      end
    end
  end

  # PUT /topics/1
  # PUT /topics/1.xml
  def update
   @topic = @forum.topics.find(params[:id])  # Edit: @topic = Topic.find(params[:id])

    respond_to do |format|
      if @topic.update_attributes(params[:topic])
        flash[:notice] = 'Topic was successfully updated.'
       format.html { redirect_to(@forum) }  # Edit: format.html { redirect_to(@topic) }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @topic.errors, :status => :unprocessable_entity }
      end
    end
  end

  # DELETE /topics/1
  # DELETE /topics/1.xml
  def destroy
   @topic = @forum.topics.find(params[:id])  # Edit: @topic = Topic.find(params[:id])
    @topic.destroy

    respond_to do |format|
     format.html { redirect_to(forum_topics_url(@forum)) }  # Edit: format.html { redirect_to(topics_url) }
      format.xml  { head :ok }
    end
  end
end

以上修改基於兩個目的：一、使得對於Topic的操作能關聯到正確的外鍵(forum_id)，二、在對Topic執行CUD操作後將能返回至相應的Forum頁面，而不是Topic頁面。

將/app/views/forums/show.html.erb

<p>
  <b>Name:</b>
  <%=h @forum.name %>
</p>

<p>
  <b>Description:</b>
  <%=h @forum.description %>
</p>


<%= link_to 'Edit', edit_forum_path(@forum) %> |
<%= link_to 'Back', forums_path %>

修改爲

<p>
  <b>Forum:</b>
  <%=h @forum.name %> - <%=h @forum.description %>
</p>

<% unless @forum.topics.empty? %>
  <h2>Topics</h2>
  <% @forum.topics.each do |topic| %>
    <b><%= link_to topic.subject, [@forum, topic] %></b><br />    
  <% end %>
<% end %>

<h2>New Post</h2>
<%= render :partial => @topic = Topic.new, :locals => { :button_name => 'Create' } %>

<%= link_to 'Edit', edit_forum_path(@forum) %> |
<%= link_to 'Back', forums_path %>

可以看到/app/views/topics/new.html.erb和/app/views/topics/edit.html.erb相當類似，我們創建一個新的文件/app/views/topics/_topic.html.erb

<% form_for([@forum, @topic]) do |f| %>
  <p>
    <b>Subject</b><br />
    <%= f.text_field :subject %>
  </p>

  <p>
    <b>Body</b><br />
    <%= f.text_area :body %>
  </p>

  <p>
    <%= f.submit button_name %>
  </p>
<% end %>

將/app/views/topics/new.html.erb

<h1>New topic</h1>

<% form_for(@topic) do |f| %>
  <%= f.error_messages %>

  <p>
    <%= f.label :forum %><br />
    <%= f.text_field :forum %>
  </p>
  <p>
    <%= f.label :user %><br />
    <%= f.text_field :user %>
  </p>
  <p>
    <%= f.label :subject %><br />
    <%= f.text_field :subject %>
  </p>
  <p>
    <%= f.label :body %><br />
    <%= f.text_area :body %>
  </p>
  <p>
    <%= f.submit "Create" %>
  </p>
<% end %>

<%= link_to 'Back', topics_path %>

修改爲

<h1>New topic</h1>

<%= error_messages_for :topic %>

<%= render :partial => @topic, :locals => { :button_name => "Create" } %>

<%= link_to 'Back', topics_path %>

將/app/views/topics/edit.html.erb

<h1>Editing topic</h1>

<% form_for(@topic) do |f| %>
  <%= f.error_messages %>

  <p>
    <%= f.label :forum %><br />
    <%= f.text_field :forum %>
  </p>
  <p>
    <%= f.label :user %><br />
    <%= f.text_field :user %>
  </p>
  <p>
    <%= f.label :subject %><br />
    <%= f.text_field :subject %>
  </p>
  <p>
    <%= f.label :body %><br />
    <%= f.text_area :body %>
  </p>
  <p>
    <%= f.submit "Update" %>
  </p>
<% end %>

<%= link_to 'Show', @topic %> |
<%= link_to 'Back', topics_path %>

修改爲

<h1>Editing topic</h1>

<%= error_messages_for :topic %>

<%= render :partial => @topic, :locals => { :button_name => "Submit" } %>

<%= link_to 'Show', [@forum, @topic] %> |
<%= link_to 'Back', topics_path %>

目前部分已完成Forum和Topic的關聯，以下是操作頁面截圖：
[b]Forum List[/b]
[img]/upload/attachment/43477/76cf0cd4-1727-351b-9095-ff692e40b1ab.jpg[/img]

[b]Topic List[/b]
[img]/upload/attachment/43479/26f8421f-21ef-393f-963e-02f6e5e84a59.jpg[/img]

[b]Topic Details[/b]
[img]/upload/attachment/43481/72e37cfc-5355-3ec1-97f4-d874890336d1.jpg[/img]