Design patterns: observer pattern
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The document discusses the Observer pattern in Ruby. It describes the Observer pattern as allowing one object to notify other "interested" objects when its state changes. It provides an example using the Observable module to implement the pattern. In the example, a Person object notifies an Alert observer whenever send_email is called by calling the notify_observers method, which loops through the observers and calls their gotcha method.
![module Subject
attr_reader :observers
def initialize
@observers = []
end
def add_observer(*observers)
observers.each { |observer| @observers << observer }
end
private
def notify_observers
observers.each { |observer| observer.gotcha(self) }
end
end](https://image.slidesharecdn.com/aqobihhgs2gqqkybfzfk-signature-42e3aa9a4b854966670fd4a48aba65fca994dfa394556e90b32d7ec4c235cf88-poli-160926120013/85/Design-patterns-observer-pattern-8-320.jpg)
Design patterns: observer pattern
- 1. Design Patterns in Ruby Observer Pattern Copyright 2016. Jyaasa Technologies. All Right Reserved http://jyaasa.com
- 2. Neha Suwal Associate Software Engineer at Jyaasa Technologies
- 3. Design Patterns Design principles are core abstract principles which we are supposed to follow while designing software architect
- 4. Observer Pattern: ● one object to inform other ‘interested’ objects when its state changes The Observable module in the Ruby standard library provides the mechanism necessary for us to implement this pattern, and it is fairly easy to use.
- 5. Example: module Email extend self def send(subject, receiver) mail to: “#{receiver}@example.com”, subject: “#{subject}” end end class Person include Email attr_reader :name def initialize(name) @name = name end def send_email(subject, receiver) Email.send(subject, receiver) end end
- 6. bill = Person.new 'Bill' bill.send_email 'Fishing Trip', 'Fred'
- 7. class Alert def gotcha(person) puts "!!! ALERT: #{person} SENT AN EMAIL !!!" end end
- 8. module Subject attr_reader :observers def initialize @observers = [] end def add_observer(*observers) observers.each { |observer| @observers << observer } end private def notify_observers observers.each { |observer| observer.gotcha(self) } end end
- 9. class Person include Email, Subject attr_reader :name def initialize(name) # 'super' requires a parentheses because we're calling # super on the superclass, 'Subject' super() @name = name end def send_email(subject, receiver) Email.send(subject, receiver) notify_observers end end
- 10. alert = Alert.new bill = Person.new 'Bill' bill.add_observer alert bill.send_email 'Fishing Trip', 'Fred' !!! ALERT: BILL SENT AN EMAIL !!!
- 11. THANK YOU!