From: nornagon <nornagon@...>
Date: 2005-07-05T15:23:48+09:00
Subject: Re: Observer patch

On 7/5/05, nornagon <nornagon@gmail.com> wrote:
> Hi all.
> 
> A while ago, I was playing with some network programming, and found
> that I wanted to have a class that would observe two other Observable
> classes. I could have done this by sending another parameter with
> notify_observers specifying which class the update came from -- but
> that is, to say the least, ugly. So I came up with this patch.
> (attached)
> 
> What it does is allow you to append a paramter to add_observer.
> Observable will then take that paramater and use it instead of the
> default :update -- that means you can have one Observable class call
> #update_class1 on your class and have the next call #update_class2.
> 
> Originally I kept the internal list of observers as an array and kept
> the method to send in a class variable, but that pollutes the
> namespace further and does not allow for multiple classes observing
> the same class to use different method names. So I moved the list of
> observers to a hash, that each class could have its own method called.
> 
> Without further ado, I present The Patch.

Hmm, I just noticed that the patch appears as a big unreadable string
of letters and numbers on ruby-talk.org, so here it is in plain text.

--- observer.rb	2005-07-05 09:28:14.452114352 +1000
+++ observer-new.rb	2005-07-05 09:36:49.987741024 +1000
@@ -120,12 +120,12 @@
   # Add +observer+ as an observer on this object. +observer+ will now receive
   # notifications.
   #
-  def add_observer(observer)
-    @observer_peers = [] unless defined? @observer_peers
-    unless observer.respond_to? :update
-      raise NoMethodError, "observer needs to respond to `update'" 
+  def add_observer(observer, func=:update)
+    @observer_peers = {} unless defined? @observer_peers
+    unless observer.respond_to? func
+      raise NoMethodError, "observer does not respond to `#{func.to_s}'" 
     end
-    @observer_peers.push observer
+    @observer_peers[observer] = func
   end
 
   #
@@ -181,9 +181,9 @@
   def notify_observers(*arg)
     if defined? @observer_state and @observer_state
       if defined? @observer_peers
-	for i in @observer_peers.dup
-	  i.update(*arg)
-	end
+	@observer_peers.each { |k, v|
+      k.send v, *arg
+    }
       end
       @observer_state = false
     end

-- 
- nornagon