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
2. Rivu Chakraborty BYJU’S @rivuchakraborty Efficient Async Coding in Kotlin Coroutines
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)
4. @rivuchakraborty
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
6. Efficient Async Coding in Kotlin Coroutines Async => Concurrency
7. Concurrency • Ability to execute multiple code blocks at the same time @rivuchakraborty #DevFestAhm
8. Concurrency • Ability to execute multiple code blocks at the same time • Not only for Android Developers @rivuchakraborty #DevFestAhm
9. Concurrency • Ability to execute multiple code blocks at the same time • Not only for Android Developers • JavaScript - Promise • JVM, Android - Threads @rivuchakraborty #DevFestAhm
10. 10 Concurrency in Android • AsyncTask • CompletableFuture • Runnable / Thread (Custom Threadpool) • Rx • Counting... @rivuchakraborty #DevFestAhm
11. 11 Concurrency in Android • AsyncTask @rivuchakraborty #DevFestAhm
12. 12 Concurrency in Android • CompletableFuture @rivuchakraborty #DevFestAhm
13. 13 Concurrency in Android • Runnable / Thread @rivuchakraborty #DevFestAhm
14. 14 Concurrency in Android • Rx @rivuchakraborty #DevFestAhm
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.
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).
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.
18. Coroutines 18 @rivuchakraborty #DevFestAhm Easy to Use
19. Suspension & Continuation Builders Suspending Functions End Coroutines Components Scope & Dispatchers @rivuchakraborty #DevFestAhm
20. Coroutines 20 @rivuchakraborty #DevFestAhm Suspending vs Blocking
21. Coroutines 21 @rivuchakraborty #DevFestAhm Suspending vs Blocking
22. Coroutines 22 @rivuchakraborty #DevFestAhm Suspending vs Blocking
23. Launch a Coroutine 23 @rivuchakraborty #DevFestAhm
24. Get the Job done or cancel it, your choice. :) 24 @rivuchakraborty #DevFestAhm
25. Compute Async(hrounously) 25 @rivuchakraborty #DevFestAhm
26. Deferred 26 @rivuchakraborty #DevFestAhm • Deferred Extends Job • Wrapper around your data
27. Suspending Function 27 @rivuchakraborty #DevFestAhm • suspend is a Keyword in Kotlin
28. Suspending Function 28 @rivuchakraborty #DevFestAhm • suspend is a Keyword in Kotlin • Compiler level restriction - can’t call suspend function outside CoroutineScope
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
30. Coroutine Scope 30 @rivuchakraborty #DevFestAhm • Container of CoroutineContext
31. Coroutine Scope 31 @rivuchakraborty #DevFestAhm • Container of CoroutineContext • Every Coroutine Builder is an extension over CoroutineScope, and thus inherits its CoroutineContext
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
33. Coroutine Scope 33 @rivuchakraborty #DevFestAhm
34. Dispatchers 34 @rivuchakraborty #DevFestAhm • Determines which Thread / ThreadPool, the coroutine will run on. • Similar to the Rx Schedulers
35. Let’s Build for Android
36. Repository 36 @rivuchakraborty #DevFestAhm
37. API (Retrofit) 37 @rivuchakraborty #DevFestAhm
38. Activity 38 @rivuchakraborty #DevFestAhm
39. Call it 39 @rivuchakraborty #DevFestAhm
40. Handle Exception (Gracefully) :) 40 @rivuchakraborty #DevFestAhm
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
42. Rivu Chakraborty, BYJU’S @rivuchakraborty Thank you!