Slides from the first Rhein-Neckar Dev Meetup.

1. 1 ••
Rhein-Neckar Dev Meetup #1

2. 2 ••
Asynchronous progamming in Kotlin with Coroutines
🍕 🍕 🍕
Tensorflowing like a pro - without a clue

3. 3 ••
Coroutines
Asynchronous programming in Kotlin

4. 4 ••
How programming works
Intro
Do something (create a resource)
↓
Wait (for completion)
↓
Do something (send it to backend)
↓
Wait (for the response)
↓
Do something (process response or try again)
↓
…

5. 5 ••
Dealing with long running tasks
Asynchronicity
- Direct style
- max 16 ms
- Blocking the main Thread
- Callback
- Error Handling
- Callback Hell
- Futures (RxJava, Promises, …)
- Idea: we wrap the result
- Pro: nice code, errors, good looking
- cons: complex
- Coroutines
- Direct style

6. 6 ••
What is a Coroutine?
- It’s an instance of a suspendable computation
- General concept was already created in 1958
- Similar to a very lightweight Thread – cheap in creation
- Looks like regular blocking code
- Coroutines give us a way to write code that feels imperative, even if it is asynchronous.

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Suspend functions
- A function ‘super powers’
- It’s a function which can suspend and return a value later on

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Suspend functions II
- Suspension points
- Many things work out-of-the box
- Loops
- Exceptions
- Higher-Order-Functions
- …

9. 9 ••
suspension functions are designed to
imitate sequential behavior by default

10. 10 ••
Setup

11. 11 ••
Demo I
- Sample + Performance

12. 12 ••
https://www.slideshare.net/elizarov/deep-dive-into-coroutines-on-jvm-kotlinconf-2017
Coroutines in detail

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20. 20 ••
Reuse closure / state object
State Machine vs Callbacks
Easier loop

21. 21 ••
Suspending functions cannot be invoked from
regular functions
• launch (fire and forget)
• async (and await)
• Returns a Deferred
• runBlocking
• Not keywords but functions!
Coroutine Builder

22. 22 ••
Demo II
– Coroutine Builders

23. 23 ••
Coroutine Context
- *without*
- UI
- CommonPool
- Unconfined

24. 24 ••
Demo III
– Channels and Actors
- Comparison RX

25. 25 ••
Questions?
Pizza?

26. 26 ••
Links & References
- Coroutines guide Informal
- https://github.com/Kotlin/kotlin-coroutines/blob/master/kotlin-coroutines-informal.md
- Coroutine guide reactive
- https://github.com/Kotlin/kotlinx.coroutines/blob/master/reactive/coroutines-guide-reactive.md
- Deep dive into Coroutines on JVM, KotlinConf 2017 – Roman Elizarov
https://www.slideshare.net/elizarov/deep-dive-into-coroutines-on-jvm-kotlinconf-2017
- Images from https://www.pexels.com