Module: ActiveModel::Observing::ClassMethods

Included in:
ActiveRecord::Base
Defined in:
lib/rails/observers/active_model/observing.rb

Instance Method Summary collapse

Instance Method Details

#add_observer(observer) ⇒ Object

Add a new observer to the pool. The new observer needs to respond to update, otherwise it raises an ArgumentError exception.

class Foo
  include ActiveModel::Observing
end

class FooObserver < ActiveModel::Observer
end

Foo.add_observer(FooObserver.instance)

Foo.observers_instance
# => [#<FooObserver:0x007fccf55d9390>]



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# File 'lib/rails/observers/active_model/observing.rb', line 125

def add_observer(observer)
  unless observer.respond_to? :update
    raise ArgumentError, "observer needs to respond to 'update'"
  end
  observer_instances << observer
end

#count_observers ⇒ Object

count_observers is deprecated. Use #observers_count.



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# File 'lib/rails/observers/active_model/observing.rb', line 173

def count_observers
  msg = "count_observers is deprecated in favor of observers_count"
  ActiveSupport::Deprecation.warn(msg)
  observers_count
end

#instantiate_observers ⇒ Object

Instantiate the global observers.

class Foo
  include ActiveModel::Observing

  attr_accessor :status
end

class FooObserver < ActiveModel::Observer
  def on_spec(record, *args)
    record.status = true
  end
end

Foo.observers = FooObserver

foo = Foo.new
foo.status = false
foo.notify_observers(:on_spec)
foo.status # => false

Foo.instantiate_observers # => [FooObserver]

foo = Foo.new
foo.status = false
foo.notify_observers(:on_spec)
foo.status # => true



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# File 'lib/rails/observers/active_model/observing.rb', line 107

def instantiate_observers
  observers.each { |o| instantiate_observer(o) }
end

#notify_observers(*args) ⇒ Object

Fires notifications to model’s observers.

def save
  notify_observers(:before_save)
  ...
  notify_observers(:after_save)
end

Custom notifications can be sent in a similar fashion:

notify_observers(:custom_notification, :foo)

This will call custom_notification, passing as arguments the current object and :foo.



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# File 'lib/rails/observers/active_model/observing.rb', line 146

def notify_observers(*args)
  observer_instances.each { |observer| observer.update(*args) }
end

#observer_instances ⇒ Object

Returns the current observer instances.

class Foo
  include ActiveModel::Observing

  attr_accessor :status
end

class FooObserver < ActiveModel::Observer
  def on_spec(record, *args)
    record.status = true
  end
end

Foo.observers = FooObserver
Foo.instantiate_observers

Foo.observer_instances # => [#<FooObserver:0x007fc212c40820>]



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# File 'lib/rails/observers/active_model/observing.rb', line 76

def observer_instances
  @observer_instances ||= []
end

#observers ⇒ Object

Gets an array of observers observing this model. The array also provides enable and disable methods that allow you to selectively enable and disable observers (see ActiveModel::ObserverArray.enable and ActiveModel::ObserverArray.disable for more on this).

class ORM
  include ActiveModel::Observing
end

ORM.observers = :cacher, :garbage_collector
ORM.observers       # => [:cacher, :garbage_collector]
ORM.observers.class # => ActiveModel::ObserverArray



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# File 'lib/rails/observers/active_model/observing.rb', line 54

def observers
  @observers ||= ObserverArray.new(self)
end

#observers=(*values) ⇒ Object

Activates the observers assigned.

class ORM
  include ActiveModel::Observing
end

# Calls PersonObserver.instance
ORM.observers = :person_observer

# Calls Cacher.instance and GarbageCollector.instance
ORM.observers = :cacher, :garbage_collector

# Same as above, just using explicit class references
ORM.observers = Cacher, GarbageCollector

Note: Setting this does not instantiate the observers yet. instantiate_observers is called during startup, and before each development request.



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# File 'lib/rails/observers/active_model/observing.rb', line 38

def observers=(*values)
  observers.replace(values.flatten)
end

#observers_count ⇒ Object

Returns the total number of instantiated observers.

class Foo
  include ActiveModel::Observing

  attr_accessor :status
end

class FooObserver < ActiveModel::Observer
  def on_spec(record, *args)
    record.status = true
  end
end

Foo.observers = FooObserver
Foo.observers_count # => 0
Foo.instantiate_observers
Foo.observers_count # => 1



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# File 'lib/rails/observers/active_model/observing.rb', line 168

def observers_count
  observer_instances.size
end