code snippets for "Using C#-style Events In Ruby" post

s1.rb

class Event
 
    attr_reader :name
 
    def initialize(name)
        @name = name
        @handlers = []
    end
 
    def +(eventhandler)
        raise TypeError "Method expected" unless eventhandler.is_a? Method
        @handlers[@handlers.size] = eventhandler
        self
    end
     
    def -(eventhandler)
        @handlers.delete eventhandler
        self
    end
     
    def trigger(args)
        @handlers.each { |handler| handler.call args }
    end
     
end

s2.rb

publisher.some_event += method(:my_event_handler)

s3.rb

publisher.some_event -= method(:my_event_handler)

s4.rb

class Object
     
    private
     
    def define_event(symbol)
        getter = symbol
        setter = :"#{symbol}="
        variable = :"@#{symbol}"
 
        define_method getter do
            event = instance_variable_get variable
             
            if event == nil
                event = Event.new(symbol.to_s)
                instance_variable_set variable, event
            end
             
            event
        end
         
        define_method setter do |value|
            instance_variable_set variable, value
        end
    end
 
    def trigger_event(symbol, args)
        event = instance_variable_get :"@#{symbol}"
        event.trigger *args
    end
     
end

s5.rb

publisher.some_event += method(:my_event_handler)

s6.rb

publisher.some_event = publisher.some_event + method(:my_event_handler)

s7.rb

class Publisher
    define_event :notify
     
    def trigger_notify
        trigger_event :notify, "hello world!"
    end
     
end

s8.rb

class Subscriber
     
    def start_listening_to(publisher)
        raise TypeError "Publisher expected" unless publisher.is_a? Publisher
        @publisher = publisher
        @publisher.notify += method(:event_handler)
    end
 
    def stop_listening
        @publisher.notify -= method(:event_handler)
        @publiser = nil
    end
     
    def event_handler(args)
        puts "#{object_id} #{Time.now} received: #{args}"
    end
     
end

s9.rb

publisher = Publisher.new
subscriber1 = Subscriber.new
subscriber2 = Subscriber.new
subscriber1.start_listening_to publisher
subscriber2.start_listening_to publisher
publisher.trigger_notify
subscriber1.stop_listening
publisher.trigger_notify