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POHow can I improve the hierarchy of my event classes?
 

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  1. POHow can I improve the hierarchy of my event classes?
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    <p>For the <a href="https://meta.stackexchange.com/questions/57316/offer-an-xmpp-method-for-chat/63420#63420">XMPP interface for the Stack Overflow chat</a> I am parsing the JSON feed from chat and generating Ruby objects for every chat events, such as messages sent, edits sent, users logging in or out, etc. I also generate events for "slash-commands" sent to the XMPP server, like "/help" or "/auth" in order to allow the XMPP user to authenticate with their Stack Overflow chat account.</p> <p>I have set up these classes in a hierarchy I feel makes good logical sense:</p> <pre><code>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) </code></pre> <p>You can see the full hierarchy and source <a href="http://trac.digitalfruition.com/soxmpp/browser/trunk/classes/SOChatEvents.rb" rel="nofollow noreferrer">in Trac</a> or <a href="https://svn.smart-safe-secure.com/soxmpp/trunk/classes/SOChatEvents.rb" rel="nofollow noreferrer">via SVN</a>.</p> <p>My question is twofold: First, what is the best way to instantiate these events? What I'm currently doing is parsing the JSON events using a giant <code>switch</code> statement --well, it's ruby so it's a <code>case</code> statement -- and, it's not giant <em>yet</em>, but it will be if I continue this way:</p> <pre><code>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 </code></pre> <p>But I imagine there has to be a better way to handle that! Something like <code>SOChatEvent.createFromJSON( json_data )</code>... But, what's the best way to structure my code so that objects of the proper subclass are created in response to a given <code>event_type</code>?</p> <p>Second, I'm not actually using ant subclasses of <code>SOXMPPUserCommand</code> yet. Right now all commands are just instances of <code>SOXMPPUserCommand</code> itself, and that class has a single <code>execute</code> method which switches based upon regex of the command. Much the same problem -- I know there's a better way, I just am not sure what the best way is:</p> <pre><code>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 </code></pre> <p>and:</p> <pre><code>class SOXMPPUserCommand &lt; SOXMPPMessage def execute case @body when "/help" "Available topics are: help auth /fkey /cookie\n\nFor information on a topic, send: /help &lt;topic&gt;" 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 &lt;fkey&gt;. Displays or sets your fkey, used for authentication. Send '/fkey' alone to display your current fkey, send '/fkey &lt;something&gt;' to set your fkey to &lt;something&gt;. You can obtain your fkey via the URL: javascript:alert(fkey().fkey)" when "/help /cookie" "Usage: /cookie &lt;cookie&gt;. Displays or sets your cookie, used for authentication. Send '/cookie' alone to display your current fkey, send '/cookie &lt;something&gt;' to set your cookie to &lt;something&gt;" 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 </code></pre> <p>I know there's a better way to do this, just not sure what specifically it is. Should the responsibility of creating subclasses of <code>SOXMPPUserCommand</code> fall on <code>SOXMPPUserCommand</code> itself? Should all subclasses register with the parent? Do I need a new class?</p> <p>What's the best way to instantiate objects of subclasses in such a hierarchal structure?</p>
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