A talk I gave at DevFest21 with GDG Damanhour at the Faculty of medicine, Alexandria university. chapter on Jan 1st 2022 talking about Asynchronous Programming and different approaches like Threading, Callbacks, and Coroutines

1. A Journey from
Callback Hell
to
Kotlin Coroutines
Ahmed Nabil
Kotlin Egypt
@AhmedNMahran
Sat. Jan 1 2022

2. About Me
About Me

3. 1. Writing Code since I was 11
2. 8+ years in Mobile App development
3. Given talks to thousands of audiences
4. Prev. Android Mentor at 1M Arab Coders.
5. Worked at Hungerstation,Codly, and others.
6. Software Tech. Lead at Vodafone (_VOIS).
7. Head of Kotlin Egypt.
About Me

4. About Me
What
is Kotlin ?

5. 1. A modern Programming Language.
2. Developed by Jetbrains & Open-Source community
3. Since 2010.
4. Current Stable Version is 1.6.10 (as of 31-12-2021)
Kotlin

6. 1. Multiplatform-Mobile
2. Server-Side
3. Web Front-End
4. Android
5. WatchOS
6. Data Science
7. and more
Used to Develop

7. About Me
Let
the journey
Begin

10. ANR
● any operation > 16ms may cause Lag
● I/O operations, long running operation
● Main thread should ONLY do
UI operations

12. About Me
Asynchronous
Code

13. 1.Threading
2.Callbacks
3.Futures, Promises
4.Reactive Extensions (Rx)
5.Coroutines
Approaches

14. About Me
Problem
Code running in Main
thread causing Crash or
Lag.

15. About Me
Threads
A program splits itself
into 2 or more running
tasks

16. 1.Expensive
2.Not Infinite, limited with device capabilities
3.Not always available, (e.g. JS doesn’t have threading)
4.Hard to Error-handle and debug
Threads Limitations

18. About Me
Callbacks
a function sent as an
argument to another
function to be executed
at certain point in time.

20. 1.Nested Callbacks not easy to understand
2.Hard to Error-handle and debug
Callback Limitations

22. About Me
Futures
and Promises
I promise I’ll return at
some point in the future.

23. 1.Nested Callbacks not easy to understand
2.Return Type :
Needs changing the models (extra steps in getting the data)
3.Hard to Error-handle and debug
Limitations

24. About Me
Rx
Everything is a stream
and it’s observable
Needs learning new apis
:(

25. About Me
Coroutines
Kotlin’s approach to work
with async. code

26. Process
Thread1
Thread2
Coroutine1
Coroutine2
Coroutine3
Couroutine4

27. 1.No new apis needed, same language used (kotlin)
2.Return type doesn’t change.
3.Write sequential code while being thread-safe
4.Lightweight, can run many of them in one thread,
5.Easy to switch between threads
6.Platform independent
7.Easy to debug and detect errors.
Coroutines

29. Quiz
& Prize

30. About Me
Follow Me
@AhmedNMahran
Thanks!
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31. Thanks
Ahmed Nabil
Kotlin Egypt
@AhmedNMahran