Journey to understand Observer and Pub-Sub Pattern

Transcript

1. Journey to understand Observer
   and Pub-Sub Pattern
   
   

   View Slide

2. Let’s understand the need?
   • Derivation in a mathematical way
   

   View Slide

3. • Derive: What is observer pattern and pub sub pattern and why do
   we need them.
   
   • Given: iPhone, User, Different situations
   
   • Assumption: Let’s assume that there are no observers or pub sub
   patterns. What will happen:
   1. No real time modifying view
   controllers:
   

   View Slide

4. 2. Periodic Monitoring increases
   • Regular monitoring in regular intervals
   • Periodic networking calls
   • Periodic monitoring of different resources.
   

   View Slide

5. 3. Checking the state of resources periodically
   

   View Slide

6. • Result: Nobody wants this and thus we can say we need
   someone to tell about the change.
   

   View Slide

7. Observer pattern
   &
   Publisher-Subscriber Pattern
   

   View Slide

8. Observer Pattern
   “The observer pattern is a software design pattern in which an
   object, called the subject maintains a list of its dependents, called
   observers, and notifies automatically of any state changes, usually
   by calling one of their methods.”
   -Wikipedia
   

   View Slide

9. Pub Sub Pattern
   • Pub: Publishers
   • Sub: Subscribers
   • A software design pattern where there are senders of
   some messages and they send the messages to the
   receivers called the subscribers.
   -Unknown
   

   View Slide

10. Confusing??
    

    View Slide

11. Difference in implementation
    Observer Pattern
    

    View Slide

12. Pub-Sub Pattern
    Event Channel in between called an Event Bus or Broker
    Pub Sub Pattern
    

    View Slide

13. APIs providing such facilities
    • Notification Center
    
    • Observation Protocols
    
    • RxSwift
    
    • Grand Central Dispatch
    
    • MQTT
    
    • Delegates
    

    View Slide

14. Notification Centers
    Posting Notifications
    

    View Slide

15. Receiving the Notification
    

    View Slide

16. Receiving the Notification
    

    View Slide

17. Receiving the Notification
    

    View Slide

18. Receiving the Notification
    

    View Slide

19. Using Protocols
    

    View Slide

20. Event Bus using RxSwift
    • RxSwift
    
    • Understanding of Reactive Programming
    
    • Publish Subjects
    

    View Slide

21. Publish Subjects
    • Subjects: Observable + Observer
    • It emits all the subsequent items of the source
    Observable at the time of subscription.
    

    View Slide

22. Use case
    • Event Bus to broadcast the subscribers about the events of
    your journey.
    • Beginning of journey
    • Ending of Journey
    • Journey updates
    • Any journey related channel
    

    View Slide

23. Steps to success!!
    • Create some dummy locations
    • Create a singleton class to set the Journey Events and get
    the journey events
    

    View Slide

24. Steps to success!!
    • Create some dummy locations
    • Create a singleton class to set the Journey Events and get
    the journey events
    

    View Slide

25. Steps to success!!
    • Create some dummy locations
    • Create a singleton class to set the Journey Events and get
    the journey events
    

    View Slide

26. Steps to success!!
    • Create some dummy locations
    • Create a singleton class to set the Journey Events and get
    the journey events
    

    View Slide

27. • Subscribe to the “Resource” in viewDidLoad( )
    • Now you can get the events wherever you write this
    subscribe code
    

    View Slide

28. • Subscribe to the “Resource” in viewDidLoad( )
    • Now you can get the events wherever you write this
    subscribe code
    

    View Slide

29. • Subscribe to the “Resource” in viewDidLoad( )
    • Now you can get the events wherever you write this
    subscribe code
    

    View Slide

30. Setting the events
    

    View Slide

31. Setting the events
    

    View Slide

32. Thank You #
    @droid_singh amanjeetsingh150
    

    View Slide