Efficient Async Coding in Kotlin Coroutines

Presented in #DevFestAhm #DevFest18 #DevFestIndia
Working with asynchronous code is difficult especially for Android Developers which ultimately leads to callback hell. The only way out is using Rx, but again Rx has a really steep learning curve, and forces reactive style on the developers, whether you like it or not, the problem with Rx is that, most beginners in Rx tends to mix reactive style with imperative style which causes bugs and loopholes and also debugging Rx is almost a nightmare.
Most Android developers are using Kotlin nowadays, it has many fantastic features, Coroutines being most notable among them, moreover they're stable now.
This talk would cover:
- Co-routines Generator API Example (for explaining suspension)
- How and where to create Coroutine Scopes, and how to manage them
- How to make API calls just by using co-routines and Kotlin URL extension functions
- How to use co-routines with popular REST client Retrofit.

Transcript

1. Rivu Chakraborty
   Efficient Async Coding in Kotlin
   Coroutines
   

   View Slide

2. Rivu Chakraborty
   BYJU’S
   @rivuchakraborty
   Efficient Async Coding in
   Kotlin Coroutines
   

   View Slide

3. Rivu Chakraborty
   BYJU’S
   @rivuchakraborty
   About Me
   ● Sr Software Engineer (Android) - BYJU’S
   ● Instructor - Caster.io
   ● Google Certified Associate Android Developer
   ● DroidJam Speaker
   ● Author - Reactive Programming in Kotlin
   ● Author - Functional Kotlin
   ● Author - Coroutines for Android Developers (WIP)
   

   View Slide

4. @rivuchakraborty
   

   View Slide

5. Books
   https://www.packtpub.com/application-d
   evelopment/reactive-programming-kotlin
   https://www.packtpub.com/application-de
   velopment/functional-kotlin
   https://leanpub.com/coroutines-for-andr
   oid-developers
   Work in Progress
   

   View Slide

6. Efficient Async Coding in
   Kotlin Coroutines
   Async => Concurrency
   

   View Slide

7. Concurrency
   ● Ability to execute
   multiple code blocks
   at the same time
   @rivuchakraborty
   #DevFestAhm
   

   View Slide

8. Concurrency
   ● Ability to execute
   multiple code blocks at
   the same time
   ● Not only for Android
   Developers
   @rivuchakraborty
   #DevFestAhm
   

   View Slide

9. Concurrency
   ● Ability to execute multiple
   code blocks at the same time
   ● Not only for Android
   Developers
   ● JavaScript - Promise
   ● JVM, Android - Threads
   @rivuchakraborty
   #DevFestAhm
   

   View Slide

10. 10
    Concurrency in Android
    ● AsyncTask
    ● CompletableFuture
    ● Runnable / Thread (Custom Threadpool)
    ● Rx
    ● Counting...
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

11. 11
    Concurrency in Android
    ● AsyncTask
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

12. 12
    Concurrency in Android
    ● CompletableFuture
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

13. 13
    Concurrency in Android
    ● Runnable / Thread
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

14. 14
    Concurrency in Android
    ● Rx
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

15. 15
    Concurrency in Android
    ● Coroutines
    @rivuchakraborty
    #DevFestAhm
    Let’s you write non-blocking asynchronous code in your
    choice of Style - Sequentially, in Functional Style or whatever
    you prefer.
    

    View Slide

16. Coroutines
    16
    @rivuchakraborty
    #DevFestAhm
    Light-Weight Threads
    Thread 1 Thread 2 Thread 3
    Coroutine 1 Coroutine 2 Coroutine 3
    With Coroutines, Threads are still used (for JVM).
    

    View Slide

17. Coroutines
    17
    @rivuchakraborty
    #DevFestAhm
    Light-Weight Threads
    Thread 1 Thread 2 Thread 3
    Coroutine 1 Coroutine 2 C 3 C 4 C 5 C 6 C 7 C 8 C N
    But a single Coroutine can run multiple coroutines.
    

    View Slide

18. Coroutines
    18
    @rivuchakraborty
    #DevFestAhm
    Easy to Use
    

    View Slide

19. Suspension &
    Continuation
    Builders
    Suspending
    Functions
    End
    Coroutines
    Components
    Scope &
    Dispatchers
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

20. Coroutines
    20
    @rivuchakraborty
    #DevFestAhm
    Suspending vs
    Blocking
    

    View Slide

21. Coroutines
    21
    @rivuchakraborty
    #DevFestAhm
    Suspending vs
    Blocking
    

    View Slide

22. Coroutines
    22
    @rivuchakraborty
    #DevFestAhm
    Suspending vs
    Blocking
    

    View Slide

23. Launch a Coroutine
    23
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

24. Get the Job done or cancel it, your
    choice. :)
    24
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

25. Compute Async(hrounously)
    25
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

26. Deferred
    26
    @rivuchakraborty
    #DevFestAhm
    ● Deferred
    Extends Job
    ● Wrapper
    around your
    data
    

    View Slide

27. Suspending Function
    27
    @rivuchakraborty
    #DevFestAhm
    ● suspend is a
    Keyword in Kotlin
    

    View Slide

28. Suspending Function
    28
    @rivuchakraborty
    #DevFestAhm
    ● suspend is a Keyword in
    Kotlin
    ● Compiler level
    restriction - can’t
    call suspend
    function outside
    CoroutineScope
    

    View Slide

29. Suspending Function
    29
    @rivuchakraborty
    #DevFestAhm
    ● suspend is a Keyword in
    Kotlin
    ● Compiler level restriction -
    can’t call suspend function
    outside CoroutineScope
    ● Suspends
    execution of
    current coroutine
    

    View Slide

30. Coroutine Scope
    30
    @rivuchakraborty
    #DevFestAhm
    ● Container of
    CoroutineContext
    

    View Slide

31. Coroutine Scope
    31
    @rivuchakraborty
    #DevFestAhm
    ● Container of
    CoroutineContext
    ● Every Coroutine
    Builder is an
    extension over
    CoroutineScope,
    and thus inherits its
    CoroutineContext
    

    View Slide

32. Coroutine Scope
    32
    @rivuchakraborty
    #DevFestAhm
    ● Container of
    CoroutineContext
    ● Every Coroutine Builder is an
    extension over
    CoroutineScope, and thus
    inherits its CoroutineContext
    ● All Coroutines must
    be launched within
    a CoroutineScope
    

    View Slide

33. Coroutine Scope
    33
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

34. Dispatchers
    34
    @rivuchakraborty
    #DevFestAhm
    ● Determines which Thread / ThreadPool, the
    coroutine will run on.
    ● Similar to the Rx Schedulers
    

    View Slide

35. Let’s Build for
    Android
    

    View Slide

36. Repository
    36
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

37. API (Retrofit)
    37
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

38. Activity
    38
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

39. Call it
    39
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

40. Handle Exception (Gracefully) :)
    40
    @rivuchakraborty
    #DevFestAhm
    

    View Slide

41. Rivu Chakraborty, BYJU’S
    @rivuchakraborty
    Resources
    https://caster.io/courses/kotlin-c
    oroutines-fundamentals
    ● http://bit.ly/CodeLabCoroutines
    ● http://bit.ly/CoroutinesAndroid
    ● http://bit.ly/DroidCoroutines
    ● http://bit.ly/CoroutinesGuide
    

    View Slide

42. Rivu Chakraborty, BYJU’S
    @rivuchakraborty
    Thank you!
    

    View Slide