Class: Pokan::EventHandler

Inherits:
Object
  • Object
show all
Defined in:
lib/pokan/event_handler.rb

Overview

EventHandler is a class that associate blocks with events, making it possible to emit events and executing all the related callbacks (sequentially, in the order they were registered).

Usage

e = EventHandler.new
e.register(:my_event) { puts 'oh my!' }
e.events                     #=> [:my_event]
e.subscribers(:my_event)     #=> Proc array with callbacks
e.emit(:my_event)            #=> 'oh my!' is printed

Instance Method Summary collapse

Constructor Details

#initialize ⇒ EventHandler

creates a new instance of EventHandler, ready for event registrations



22
23
24
 
# File 'lib/pokan/event_handler.rb', line 22

def initialize
  @callbacks = {}
end

Instance Method Details

#emit(event, options = {}) ⇒ Object

Emits the given event, thus calling all the registered callbacks up to that point. If there are no registered callbacks for the event passed, nothing is done.

If the registered callbacks expected parameters, pass them using the with option

 e = EventHandler.new
 e.register(:awesome) { puts 'awesome!' }
 e.register(:awesome) { puts 'not that awesome...' }
 e.emit(:awesome)    #=> messages are print

Using the +with+ option:

 e = EventHandler.new
 e.register(:awesome) { |msg| puts msg }
 e.emit(:awesome, :with => ['awesome!']) #=> 'awesome!' is print



88
89
90
91
92
93
94
95
96
97
98
 
# File 'lib/pokan/event_handler.rb', line 88

def emit(event, options = {})
  raise_unless_symbol(event)

  args = options[:with] || []
  
  if @callbacks.has_key? event
    @callbacks[event].each { |c| c.call(*args) }
  end

  self
end

#events ⇒ Object

Retrieves the names of all the events for which there is at least one associated callback



49
50
51
 
# File 'lib/pokan/event_handler.rb', line 49

def events
  @callbacks.keys
end

#register(event, &block) ⇒ Object

register is the method used to associate a block with an event. The event name must be passed as a symbol, otherwise an exception is raised. You can call register on the same event any number of times, but it is important to note that the blocks associated will be called in the same order they were registered.

e = EventHandler.new
e.register(:my_event) { puts 'my event' }.register(:my_event) { puts 'is cool!' }

Raises:



36
37
38
39
40
41
42
43
44
 
# File 'lib/pokan/event_handler.rb', line 36

def register(event, &block)
  raise_unless_symbol(event)

  raise NoBlockGivenError, 'must provide a block' unless block_given?

  initialize_callbacks_for(event)
  @callbacks[event] << block
  self
end

#reset(event) ⇒ Object

Removes all the callbacks registered with event



63
64
65
66
67
68
 
# File 'lib/pokan/event_handler.rb', line 63

def reset(event)
  raise_unless_symbol(event)

  @callbacks.delete(event)
  self
end

#subscribers(event) ⇒ Object

Returns an array with all the Proc objects for callbacks registered for the given event



56
57
58
59
60
 
# File 'lib/pokan/event_handler.rb', line 56

def subscribers(event)
  raise_unless_symbol(event)

  @callbacks[event] || []
end