code snippets for "Using More Rubyesq Events In Ruby" post

s1.rb

class Something
    include EventPublisher
    event :some_event
end

s2.rb

something.subscribe :some_event, method(:some_handler)

s3.rb

something.subscribe(:some_event) { |args| puts "something happened!" }

s4.rb

something.unsubscribe :some_event, method(:some_handler)

s5.rb

class Event
    attr_reader :name
     
    def initialize(name)
        @name = name
        @handlers = []
    end
     
    def add(method=nil, &block)
        @handlers << method if method
        @handlers << block if block
    end
     
    def remove(method)
        @handlers.delete method
    end
     
    def trigger(*args)
        @handlers.each { |handler| handler.call *args }
    end
end

s6.rb

module EventPublisher
    def subscribe(symbol, method=nil, &block)
        event = send(symbol)
        event.add method if method
        event.add block if block
    end
 
    def unsubscribe(symbol, method)
        event = send(symbol)
        event.remove method
    end
     
    private
     
    def trigger(symbol, *args)
        event = send(symbol)
        event.trigger *args
    end
 
    self.class.class_eval do
        def event(symbol)
            getter = 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
        end
    end
end

s7.rb

class Publisher
    include EventPublisher
    event :notify
     
    def trigger_notify
        trigger :notify, "hello world!"
    end
end

s8.rb

class SubscriberWithMethod
    def start_listening_to(publisher)
        @publisher = publisher
        @publisher.subscribe :notify, method(:notify_handler)
    end
     
    def stop_listening
        @publisher.unsubscribe :notify, method(:notify_handler)
    end
     
    def notify_handler(args)
        puts "#{self.class.to_s} received: #{args}"
    end
end
 
class SubscriberWithBlock
    def start_listening_to(publisher)
        @publisher = publisher
        @publisher.subscribe(:notify) { |args| puts "block received: #{args}" }
    end
end

s9.rb

publisher = Publisher.new
subscriber1 = SubscriberWithMethod.new
subscriber2 = SubscriberWithBlock.new
subscriber1.start_listening_to publisher
subscriber2.start_listening_to publisher
publisher.trigger_notify
subscriber1.stop_listening
publisher.trigger_notify