Add Eventable.off method to cancel callbacks

README.md

@@ -666,15 +666,22 @@ idiom it is available as a public API.
 
 ```ruby
 > o = Class.new { include EM::Eventable }.new
-=> #<#<Class:0x6dc1310>:0x6dc2ec0>
+=> #<#<Class:0xab63f00>:0xab64430>
 > o.on(:november_5_1955) { puts "Ow!" }
-=> [#<Proc:0x6dc6300>]
-> o.on(:november_5_1955) { puts "Flux capacitor!" }
-=> [#<Proc:0x6dc6300>, #<Proc:0x6dc1ba0>]
+=> [#<Proc:0xad9bf00>]
+> flux = proc{ puts "Flux capacitor!" }
+=> #<Proc:0xab630f0>
+> o.on(:november_5_1955, &flux)
+=> [#<Proc:0xad9bf00>, #<Proc:0xab630f0>]
 > o.trigger(:november_5_1955)
 Ow!
 Flux capacitor!
 => [nil, nil]
+> o.off(:november_5_1955, &flux)
+=> #<Proc:0xab630f0>
+> o.trigger(:november_5_1955)
+Ow!
+=> [nil]
 ```
 
 # Suggestions?

motion/reactor/eventable.rb

@@ -7,18 +7,28 @@ module Eventable
       # and be passed the arguments that are passed to
       # `trigger`.
       def on(event, &blk)
-        @events ||= Hash.new { |h,k| h[k] = [] }
-        @events[event].push blk
+        events[event].push blk
+      end
+
+      # When `event` is triggered, do not call the given
+      # block any more
+      def off(event, &blk)
+        events[event].delete_if { |b| b == blk }
+        blk
       end
 
       # Trigger an event
       def trigger(event, *args)
-        @events ||= Hash.new { |h,k| h[k] = [] }
-        @events[event].map do |event|
+        events[event].map do |event|
           event.call(*args)
         end
       end
 
+      private
+
+      def events
+        @events ||= Hash.new { |h,k| h[k] = [] }
+      end
     end
   end
 end

spec/motion/reactor/eventable_spec.rb

@@ -15,6 +15,21 @@
       events = @subject.instance_variable_get(:@events)
       events[:foo].member?(proof).should == true
     end
+
+    it 'returns the array of blocks for the event' do
+      proof = proc {  }
+      @subject.on(:foo, &proof).should == [proof]
+    end
+  end
+
+  describe '.off' do
+    it 'unregisters events' do
+      proof = proc { }
+      @subject.on(:foo, &proof)
+      events = @subject.instance_variable_get(:@events)
+      @subject.off(:foo, &proof)
+      events[:foo].member?(proof).should == false
+    end
   end
 
   describe '.trigger' do