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如何改进事件类的层次结构?

class-hierarchy class events oop

Josh Andreas Rehm · 技术社区 · 14 年前

对于 XMPP interface for the Stack Overflow chat 我正在分析来自chat的JSON提要,并为每个聊天事件生成Ruby对象,例如发送的消息、发送的编辑、用户登录或注销等。我还为发送到XMPP服务器的“斜杠命令”生成事件,例如“/help”或“/auth”,以便XMPP用户使用其堆栈溢出的聊天帐户进行身份验证。

我已经在一个我觉得很有逻辑意义的层次结构中设置了这些类:

class SOChatEvent # base class
 |
 |--- class SOXMPPEvent # base for all events that are initiated via XMPP
 | |
 | |--- class SOXMPPMessage # messages sent to the XMPP bridge via XMPP
 | | |
 | | |--- class SOXMPPMessageToRoom # messages sent from an XMPP user to an XMPP MUC
 | | |
 | | |--- class SOXMPPUserCommand # class for "slash commands", that is, messages starting
 | | | |                          # with /, used for sending commands to the bridge
 | | | |
 | | | |--- class SOXMPPUserHelpCommand
 | | | |--- class SOXMPPUserLoginCommand
 | | | |--- class SOXMPPUserBroadcastCommand
 |
 |--- class SOChatRoomEvent # base class for all events that originate from an SO chat room
 | |
 | |--- class SOChatMessage # messages sent to an SO chat room via the SO chat system
 | | |
 | | |--- class SOChatMessageEdit # edits made to a prior SOChatMessage
 | |
 | |--- class SOChatUserEvent # events related to SO chat users
 | | |
 | | |--- class SOChatUserJoinRoom #Event for when a So user joins a room
 | | |--- class SOChatUserLeaveRoom #Event for when a So user leaves a room

 (etc)

您可以看到完整的层次结构和源 in Trac 或 via SVN .

我的问题有两个:首先,实例化这些事件的最佳方法是什么?我目前正在做的是使用一个巨大的 switch 声明——嗯,是ruby所以是 case 声明——而且,它不是巨大的然而 ,但如果我继续这样做的话:

rooms.each do |room|
  rid = "r"+"#{room.room_id}"
  if !data[rid].nil?
    @last_update = data[rid]['t'] if data[rid]['t']

    if data[rid]["e"]
      data[rid]["e"].each do |e|
        puts "DEBUG: found an event: #{e.inspect}"
        case e["event_type"]
          when 1
            event = SOChatMessage.new(room,e['user_name'])
            event.encoded_body = e['content']
            event.server = @server
            events.push event
          when 2
            event = SOChatMessageEdit.new(room,e['user_name'])
            event.encoded_body = e['content']
            event.server = @server
            events.push event
          when 3
            user = SOChatUser.new(e['user_id'], e['user_name'])
            event = SOChatUserJoinRoom.new(room,user)
            event.server = @server
            events.push event
          when 4
            user = SOChatUser.new(e['user_id'], e['user_name'])
            event = SOChatUserLeaveRoom.new(room,user)
            event.server = @server
            events.push event
        end
      end
    end
  end
end

但我想必须有更好的方法来处理这个问题!有点像 SOChatEvent.createFromJSON( json_data ) ... 但是,什么是构造我的代码的最佳方法,以便创建适当子类的对象来响应给定的 event_type ?

第二,我实际上没有使用 SOXMPPUserCommand 但是。现在所有的命令都是 SOXMPPUserCommand命令 它本身,那个类有一个 execute 方法,该方法基于命令的regex进行切换。同样的问题——我知道有更好的办法,我只是不知道最好的办法是什么:

def handle_message(msg)
    puts "Room \"#{@name}\" handling message: #{msg}"
    puts "message: from #{msg.from} type #{msg.type} to #{msg.to}: #{msg.body.inspect}"

    event = nil

    if msg.body =~ /\/.*/
      #puts "DEBUG: Creating a new SOXMPPUserCommand"
      event = SOXMPPUserCommand.new(msg)
    else
      #puts "DEBUG: Creating a new SOXMPPMessageToRoom"
      event = SOXMPPMessageToRoom.new(msg)
    end

    if !event.nil?
      event.user = get_soxmpp_user_by_jid event.from
      handle_event event
    end
  end

以及:

class SOXMPPUserCommand < SOXMPPMessage
  def execute
    case @body
      when "/help"
        "Available topics are: help auth /fkey /cookie\n\nFor information on a topic, send: /help <topic>"
      when "/help auth"
        "To use this system, you must send your StackOverflow chat cookie and fkey to the system. To do this, use the /fkey and /cookie commands"
      when "/help /fkey"
        "Usage: /fkey <fkey>. Displays or sets your fkey, used for authentication. Send '/fkey' alone to display your current fkey, send '/fkey <something>' to set your fkey to <something>. You can obtain your fkey via the URL: javascript:alert(fkey().fkey)"
      when "/help /cookie"
        "Usage: /cookie <cookie>. Displays or sets your cookie, used for authentication. Send '/cookie' alone to display your current fkey, send '/cookie <something>' to set your cookie to <something>"
      when /\/fkey( .*)?/
        if $1.nil?
          "Your fkey is \"#{@user.fkey}\""
        else
          @user.fkey = $1.strip
          if @user.authenticated?
            "fkey set to \"#{@user.fkey}\". You are now logged in and can send messages to the chat"
          else
            "fkey set to \"#{@user.fkey}\". You must also send your cookie with /cookie before you can chat"
          end
        end
      when /\/cookie( .*)?/
        if $1.nil?
          "Your cookie is: \"#{@user.cookie}\""
        else
          if $1 == " chocolate chip"
            "You get a chocolate chip cookie!"
          else
            @user.cookie = $1.strip
            if @user.authenticated?
              "cookie set to \"#{@user.cookie}\". You are now logged in and can send messages to the chat"
            else
              "cookie set to \"#{@user.cookie}\". You must also send your fkey with /fkey before you can chat"
            end
          end
        end
      else
        "Unknown Command \"#{@body}\""
    end
  end
end

我知道有更好的办法,只是不知道具体是什么。是否有责任创建 SOXMPPUserCommand命令 落下 SOXMPPUserCommand命令 它自己?所有子类都应该向父类注册吗?我需要一个新班吗?

在这种层次结构中实例化子类对象的最佳方法是什么?

1 回复 | 直到 7 年前

forforf 14 年前

回答你的第一个问题。以下是一些你可能想考虑的想法

首先,构造子类,使它们都使用相同的初始化参数。此外,您还可以将其他一些启动代码(例如您的编码体和服务器访问器)放在那里。我的意思是:

# SOChat Class skeleton structure
class SOChatSubClass  #< inherit from whatever parent class is appropriate
  attr_accessor :encoded_body, :server, :from, :to, :body

  def initialize(event, room, server)
    @encoded_body = event['content']
    @server = server
    SOChatEvent.events.push event

    #class specific code 
    xmpp_message = event['message']
    @from = xmpp_message.from
    @to = xmpp_message.to
    @body = xmpp_message.body
    #use super to call parent class initialization methods and to DRY up your code
  end
end

注意,在我的示例中,子类中仍然有重复的代码。理想情况下,您可以通过将副本放在适当的父类中来消除它。

如果在创建启动参数的公共列表时遇到问题,请更改类以接受参数列表作为哈希值{:event=>event,:room=>room,:server=>server,etc},而不是传入参数列表(event、room、server)。

不管怎样,一旦有了用于初始化类的公共参数结构,就可以更动态地初始化它们,从而不需要case语句。

class SOChatEvent
     class << self; attr_accessor :events; end
     @events = []

      @@event_parser = {
                                0 => SOChatSubClass, #hypothetical example for testing
                                1 => SOChatMessage,
                                2 => SOChatMessageEdit,
                                #etc
                              }
    def self.create_from_evt( json_event_data, room=nil, server=nil)
      event_type = json_event_data["event_type"]
      event_class =  @@event_parser[event_type]
      #this creates the class defined by class returned in the @@event_parser hash
      event_obj = event_class.new(json_event_data, room, server)
    end

    #rest of class
end

@@event_parser 包含事件类型与实现该事件类型的类之间的映射。您只需将适当的类分配给一个变量,并像对待实际的类一样对待它。

如下代码将创建适当类的对象:

event_obj = SOChatEvent.create_from_evt( json_event_data,
                                        "some room", 
                                        "some server")

注意:有进一步的优化可以做什么,我提供了更干净和更简洁,但希望这有助于你克服驼峰的情况说明。

编辑:我忘了提到类实例变量 SOChatEvent.events 使用此创建: class << self; attr_accessor :events; end @events = []

您将事件推到事件堆栈上,但我不清楚您希望栈存在于哪里,它是否是全局事件列表,或者特定于特定的类。我所做的是全局的,所以如果您希望将事件堆栈约束到某些类或实例,可以随意更改它。