루비로 작성된 옵서버
옵서버 패턴은 일부 객체들이 다른 객체들에 자신의 상태 변경에 대해 알릴 수 있는 행동 디자인 패턴입니다.
옵서버 패턴은 구독자 인터페이스를 구현하는 모든 객체에 대한 이러한 이벤트들을 구독 및 구독 취소하는 방법을 제공합니다.
복잡도:
인기도:
사용 사례들: 옵서버 패턴은 루비 코드, 특히 그래픽 사용자 인터페이스 컴포넌트들에서 매우 일반적입니다. 다른 객체들과의 클래스들과 결합하지 않고 해당 객체들에서 발생하는 이벤트들에 반응하는 방법을 제공합니다.
식별: 옵서버 패턴은 들어오는 메서드들을 목록에 저장하는 구독 메서드로 초기 식별할 수 있으며, 만약 위 구독 메서드가 목록의 객체들을 순회하고 그들의 '업데이트' 메서드를 호출하면 해당 패턴은 옵서버 패턴으로 확정지을 수 있습니다.
개념적인 예시
이 예시는 옵서버 패턴의 구조를 보여주고 다음 질문에 중점을 둡니다:
- 패턴은 어떤 클래스들로 구성되어 있나요?
- 이 클래스들은 어떤 역할을 하나요?
- 패턴의 요소들은 어떻게 서로 연관되어 있나요?
main.rb: 개념적인 예시
# The Subject interface declares a set of methods for managing subscribers.
class Subject
# Attach an observer to the subject.
def attach(observer)
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# Detach an observer from the subject.
def detach(observer)
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
# Notify all observers about an event.
def notify
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# The Subject owns some important state and notifies observers when the state
# changes.
class ConcreteSubject < Subject
# For the sake of simplicity, the Subject's state, essential to all
# subscribers, is stored in this variable.
attr_accessor :state
# @!attribute observers
# @return [Array<Observer>] attr_accessor :observers private :observers
def initialize
@observers = []
end
# List of subscribers. In real life, the list of subscribers can be stored
# more comprehensively (categorized by event type, etc.).
# @param [Observer] observer
def attach(observer)
puts 'Subject: Attached an observer.'
@observers << observer
end
# @param [Observer] observer
def detach(observer)
@observers.delete(observer)
end
# The subscription management methods.
# Trigger an update in each subscriber.
def notify
puts 'Subject: Notifying observers...'
@observers.each { |observer| observer.update(self) }
end
# Usually, the subscription logic is only a fraction of what a Subject can
# really do. Subjects commonly hold some important business logic, that
# triggers a notification method whenever something important is about to
# happen (or after it).
def some_business_logic
puts "\nSubject: I'm doing something important."
@state = rand(0..10)
puts "Subject: My state has just changed to: #{@state}"
notify
end
end
# The Observer interface declares the update method, used by subjects.
class Observer
# Receive update from subject.
def update(_subject)
raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
end
end
# Concrete Observers react to the updates issued by the Subject they had been
# attached to.
class ConcreteObserverA < Observer
# @param [Subject] subject
def update(subject)
puts 'ConcreteObserverA: Reacted to the event' if subject.state < 3
end
end
class ConcreteObserverB < Observer
# @param [Subject] subject
def update(subject)
return unless subject.state.zero? || subject.state >= 2
puts 'ConcreteObserverB: Reacted to the event'
end
end
# The client code.
subject = ConcreteSubject.new
observer_a = ConcreteObserverA.new
subject.attach(observer_a)
observer_b = ConcreteObserverB.new
subject.attach(observer_b)
subject.some_business_logic
subject.some_business_logic
subject.detach(observer_a)
subject.some_business_logic
output.txt: 실행 결과
Subject: Attached an observer.
Subject: Attached an observer.
Subject: I'm doing something important.
Subject: My state has just changed to: 1
Subject: Notifying observers...
ConcreteObserverA: Reacted to the event
Subject: I'm doing something important.
Subject: My state has just changed to: 10
Subject: Notifying observers...
ConcreteObserverB: Reacted to the event
Subject: I'm doing something important.
Subject: My state has just changed to: 2
Subject: Notifying observers...
ConcreteObserverB: Reacted to the event
