KotlinConf 2018 - Exploring Coroutines in Kotlin by Venkat Subramaniam

[@GooksanGom]

Great, It really helped to understand coroutines. BTW, It's very impressive that he could keep talking without a break while he writes several lines of codes and runs it. There must have been coroutines running in his brain.

[@canaldosouza4103]

This guy is who made me start kotlin, greet to see him in the Kotlin Conf

[@navsingh7934]

same here man

[@akashkroy]

I read his programming kotlin

[@ChetanSachdeva]

I've not seen anyone explaining the internals of coroutines better than Venkat Subramaniam.

[@ViperCinema4D]

kzbin.info/www/bejne/j6PVhnaJnpxle5o

[@navsingh7934]

he is the best speaker I have seen so far.

[@aprofromuk]

no 1 can do that :)

[@VedantRajdeep]

That's some introduction. I like how he explained the "Why?" part of the changes.

[@Codetutor-DemystifyCoding]

This well co-ordinated explanation along with live coding demonstration is simply brilliant. He makes it look simple, but let me tell you, as some one who makes tutorials on KZbin, this requires exceptional skills. Not just coding but presence of mind.

[@vasyan123]

I'm a simple man. I see Venkat Subramariam in a video title, I click.

[@chukzydee]

Venkat and/or Florina on the title is enough to make me suspend all I'm doing and click on the video.

[@salvatoreshiggerino6810]

To click is to do the needful

[@j-r-hill]

It's so true

[@AmarPoonia]

Same here.. even if I've watched it before, it's so satisfying

[@gleb.ignatev]

@@chukzydee suspend, you're saying, I see what you did here...

[@yasserakbbach7342]

I refer to Venkat's lectures whenever I get to the mood of seeking out wisdom 😌

[@benjaminrangel5313]

I love Venkat voice, it is so calming.

[@jimmyleo5414]

What a god damn pro, sometimes I need to pause to think about what he said

[@0xmg]

The buffering does that for me

[@thecoderui]

​@@0xmg So lucky!

[@norulesprateek]

What a great explanation! You know he is an absolute professional when he shows how suspend functions are sending the rest of the code (Continuation) of the function as a parameter 28:24 . Everything including async block explanation was just great. He taught me things he wasn't even trying(possibly) to cover in this conf. Thanks!

[@aksh1618]

What a legend. Solved so many queries I had about coroutines with such simple but precise and amazing explanations.

[@DF-ss5ep]

The one and only. We meet again.

[@KaranSharmak4c6]

Good examples. the multitasking while presentation using vim is incredible. !! Also the sound of claps at end of video says it all.

[@anshsachdeva850]

This was so captivating. i didn't even felt for a minute that am staring at my screen for 44 minutes. amazing presentation. Anyone reading this comment in 2021 : How to access the launch{} function in coroutines 1.5?

[@leomak7580]

the best speaker ever ) java versions are bumping, new langs come and go. but Venkat is a guy who always was with us )

[@johnyrufus]

That last example of step by step conversion from sequential -> suspend -> async did the trick for me :)

[@a0um]

Great presentation. I really appreciated the use of bare bone editors and the love coding. I wish he slowed down a bit around the crucial points but understand it's a lot to cover in the given time. Impressive how he kept going confidently despite the inevitable typos, etc. I still have some questions about coroutines but this talk really gave me some good examples to think about.

[@tak68tak]

He is really awesome. He is totally different from any other devs. It's like an entertainer or magician.

[@methodsignature]

I've never seen anyone program in VI before. It felt a bit like black magic.

[@thegreatestdao]

This guys speech is so captivating!

[@aikqboy]

He explains it so well and so simply. A very bright man.

[@dluxsoft2840]

thanks sir ,best lecture on coroutine

[@rajushingadiya2860]

Loved it

[@chrismakesgames9075]

This talk was great. Thanks Venkat!

[@jesprotech]

Extraodinarly goed presentation! Explaining everything from how we got here, why apply coroutines and the way to do that in Kotlin with great examples. I especially loved that last example where we can see how small changes in the code can make it asynchronous using coroutines. The yield example was really a great step in getting there to explain that. It really helped me to make it even more clear to me what coroutines actualy are, what they can do and where to use them.

[@antosha4e]

really like a way he explains stuff, his talk about DSLs also nice

[@mehmoodrehman6336]

Topics: 1. Parallel vs Asynchronous 0:50 (Java, Kotlin ahead of Java at least 5-years, Microservices, sequential vs parallel) coroutines make it easy to write asynchronous code. 2. Concurrency vs non-blocking 1:50 (Java example and comparison) 3. Let's examine parallel just a bit, in Java 2:30 (Java example and comparison) Parallel Stream: Structure of [functional] sequential code is the same as parallel code Coroutine: Structure of [Imperative] Synchronous code is the same as asynchronous code 4. Why not be happy with that? 5:20 5. Functional style is awesome 5:20 6. But, handling exceptions is a mess 5:44 7. Coroutines are asynchronous 6:25 launch { //launch () method } 8. From synchronous to asynchronous 9:00 Non-blocking GUI's 9. Blocking to non-blocking 10:12 10. How do coroutines work? 10:12 11. A sequential code 17:14 12. Using suspend 23:20, 24:30 Parallel Stream: Structure of [functional] sequential code is the same as parallel code Coroutine: Structure of [Imperative] Synchronous code is the same as asynchronous code 13. Doing asyn 33:00

[@andromadusnaruto1544]

Awesome. Much appreciated...👍🏾

[@hansmelo32]

Every the venkat's videos make me to want to be a better developer 💪🏿. Great explanation!

[@hassanalizadeh3492]

Amazing presentation

[@JetBrainsTV]

Thank you! Cheers!

[@harshvardhanjoshi7445]

Great explanation. Must have been took months to find/create an example code which is this simple but very informative and covers almost everything. Great job.

[@JetBrainsTV]

Glad you liked it

[@karthikrpandian]

Amazing talk. Impressed by his coding and explanation going hand in hand.

[@МихаилСошников-в9р]

Отличная информация, спасибо большое!

[@AlexPaluzzi]

One of the best talks I've watched in a long time.

[@muhammadrahmatullahrahman1534]

Venkat is such an awesome teacher

[@Nithr1s]

Just so you know, there is an error in explanation of "suspend" modifier. Explanation by Roman Elizarov could be found here: medium.com/@elizarov/blocking-threads-suspending-coroutines-d33e11bf4761

[@ashwin_mahajan]

Great great presentation. 🙌

[@JetBrainsTV]

Thank you kindly!

[@pums12]

Just loved it. Thanks for this simple explanation

[@terjemah_alquran]

excellent excellent excellent

[@igrai]

Frankly, found it quite convoluted

[@bangoker]

Great talk! I like that it was very concise, but I could offer one piece of feedback is to have longer pauses /paragraph breaks. It feels a little bit like a giant paragraph would read. There are sentences, but it there is no place to rest, its just one big big paragraph.

[@methodsignature]

Yea, it felt a bit like catching a wave. If I didn't have much coroutine experience, I'm not sure I could have followed very well. Some of that was probably the time constraint of the setting.

[@Wengelef]

Venkat Superman

[@pinoy_marites_beh]

I finally know what to do when someone asks me to put the status bar below the phone and the system back actions on top of the screen! Run for the exit!!!!!

Instead of suspend measureTime you could have made it inline, i think it would work with await 😀 really nice talk btw, finally understood coroutines

[@hhhapz]

I think the goal of the talk was to show how suspend functions make a difference, and allow thread blocking versus non-suspension functions.

[@JamielSheikh]

Excellent stuff, Venkat. Great explanations and witty humor.

[@hiteshchalise3988]

this was fantastic.

[@KiumarsAbedian]

Amazing talk, but I am curious what the setup is being used for interactive Kotlin/Java coding in vi/vim

[@NafiulIslam]

Great stuff!

[@thiagoalexandreee]

Amazing talk, thanks for the content!

[@sagarghare9829]

amazing and so engaging.

[@andre-vm]

3:10 HOLY MAMA! WATTA HELL IS GOIN' ON? (Nice talk, by the way. Good job!)

[@anmoldevgan7320]

Venkat is God of programming

[@smallufo]

Live coding! Awesome!

[@JohnPywtorak]

There are issues with this presentation, glossing over or missing key concepts. I would skip it if you are learning about coroutines. This was exploring, kinda, but really only the last 10 minutes are useful. The presenters book is decent, but this was not a good exploring talk. It appears I will be in the minority here. There are so few good coroutine talks, check out the Coroutines catch them all, best talk and maybe the only one.

[@rIyAsE]

One of the best talk on coroutines (Y)

"suspend modifier to a function makes it either asynchronous or non-blocking. " is not true according to the Roman Elizarov's article. medium.com/@elizarov/blocking-threads-suspending-coroutines-d33e11bf4761

[@mohammedalzamil7191]

yes

[@animeshroy3746]

VERY GOOD EXPLANATION...

[@StasBar]

Great presentation, great teacher!

[@HermanBovens]

I think I get coroutines now, but I'm not really sure why in the last part of the video, everything still needs to be in a launch {} block. Doesn't the suspend / async / await mechanism already make it asynchronous?

[@vyli1]

async {} can only be called from within a coroutine or a suspending function. In fact in the last example, the async call was not made from launch {} function, rather it was made from the lambda, that was passed as argument to the measure function. Since async {} can only be called from coroutine or a suspending function, he had to mark the lambda parameter from measure function as suspending. launch {} function is a coroutine builder. It hides lot of nontrivial code that you would have to write manually, if you wanted to write a coroutine.

[@HermanBovens]

@@vyli1 so the call to launch() is indeed unnecessary?

[@vyli1]

@@HermanBovens I'm sorry, I gave you a little bit misleading information. But first to answer your question, call to launch {} IS necessary. Originally I said, that async {} can only be called from coroutine or suspend function. This is not true, it can be called from wherever. However, .await() can only be called from coroutine or suspending function. Since in the code in the presentation we call .await() on result of async {} operation within lambda parameter, that lambda parameter MUST BE suspending lambda. (.await() can only be called from within a coroutine or suspending function). Since we've turned the lambda into a suspending function and we want to invoke the lambda from within measure function, we want to basically invoke a suspending function inside a nonsuspending function. That's not possible. Suspending functions can only be invoked from other suspending functions, or coroutines. Therefore, the measure function itself must be suspending. As I said before, suspend functions can only be called from within coroutines or another suspending functions. And we want to call the measure function. But measure function is suspending. Therefore we need to create a coroutine, from which we can call the measure function. That's why we do the call to launch {}. launch {} is a coroutine builder. It will build all the coroutine boilerplate code for us. So when we invoke our suspending function measure from within launch, our code will be executed within a coroutine, so the compiler will finally let us compile this code. There are other coroutine builders than launch, for example runBlocking {}, but in this case we didn't want to block the main thread, so that's why launch {} coroutine builder was chosen. When I said .await() can only be called from coroutine or another suspending function, what I mean is, compiler won't let you compile a code, where you'd want to invoke suspending function outside of a coroutine or a suspending function.

[@santanusur1265]

If getting Google's stock price took "2 seconds" and Amzn's stock price took 1 second... Then for the last example Amazon's stock price would show up earlier right ?

[@edjinretrogamer]

Meu Deus, pare 1 segundo pra respirar!!!

[@ImaginaryNumb3r]

@37:53 So this all is really just syntactic sugar for Thread pools and ComplteableFutures?

[@VivekYadav-ds8oz]

This guy literally looks like my maths professor.

[@studyonline3236]

How is he auto-filling sentences ?

[@Saketjsaket]

Which IDE is he using to show the demo?

[@abubakrjabbarov2303]

A very good explanation, thank you!

[@FrantisekNovak55]

isnt this all wrong?slapping suspend on a blocking call doesnt not make it async, its just synchronous within dispatcher thread from launch

[@antoniokomangyudistira4150]

the " A sequential code" part is hard to understand :(

[@AjithKumar-vk1fw]

👍

[@archiequinones6467]

Wow that was really good!! 😱😱 👏👏 just really wanna show my appreciation here 👏👏

[@VivekMore1]

You have the last name of Venkat spelled wrong in the title

[@JetBrainsTV]

Thank you. Fixed.

[@conorsmall1373]

what a killer mustache

[@siva_subramaniam]

Bm -16:58

[@rafihmahfooz5074]

He changed camps, first Scala, now this lol

[@jobiraw]

is this man from pragimtech.com ?

[@JetBrainsTV]

No, we don't believe so. Dr. Venkat Subramaniam is the founder of Agile Developer, Inc. agiledeveloper.com

[@harshtiwari9588]

Which editor does he use?

[@akashpatra19]

TextMate.

[@igorg.8624]

What do Coroutines offer that RxJava does not?

[@RobertGolusinski]

proandroiddev.com/kotlin-coroutines-vs-rxjava-an-initial-performance-test-68160cfc6723

[@robchr]

It doesn't offer anything that RxJava cannot do. Coroutines can easily represent RxJava's Single and Maybe contexts but does not handle Observable streams without additional boilerplate. For some use cases where there would be a large number of concurrent requests like a server that has 100k+ concurrent connections, coroutines could be more memory efficient since it requrires less intermediate objects (lambdas). Coroutines represent a single chain in a single object that acts like a state machine.

[@igorg.8624]

... although I must say - sequence continuations in Coroutines are super simple to reason about and much easier to teach to a newbie than RxJava

[@GK-rl5du]

It doesn't offer anything new as compared with RxJava or even any callback+eventloop models. The main promise of coroutines is that one can write syncrhonous looking code which the runtime executes concurrently. On the other hand, consider Rx... one has to be familiar with the core Rx interfaces like Observable... although this approach was much better than callback hell.. esp considering exception handling.. there's still a learning curve. Coroutines on the other hand will bring concurrency to where you are.

[@FrantisekNovak55]

I love rx, but flatmapping singles is stupid and you need to always return tuples everywhere like an idiot

[@jakubgwozdz2780]

What is that, well, IDE?

[@meribold]

That's a text editor. Probably TextMate.

[@jakubgwozdz2780]

I like the way it displays output at cursor.

[@akashpatra19]

@@jakubgwozdz2780 Yes, you have to configure. Long back after I saw his talk on Java Streams, I also configured like that. :)

[@jayasome199]

27:00 Only moment, I can laugh.

[@jayasome199]

28:30 suspend bytecode -> Continuation

[@maxchin2]

He need pauses.

[@syedtayyabulmazhar6945]

He is coding and explaining at the same time. He is so async.

[@_dinesh]

TBH, Very hard to follow. Keep the sentences simple and the example simpler.

[@sundeepsharma6782]

Sir, with due respect u have very nice knowledge but ur are speaking very fast, and hard to catch you and i lost my interest.

[@nO_d3N1AL]

Not his best talk. Surprised and disappointed that he didn't compare coroutines to using threads directly and Futures. He didn't really say what co-routines add that we can't do since Java 5

[@pradeepkumarreddykondreddy7048]

this guy is too fast

[@RameshK-dy6yb]

for simple basics kzbin.info/www/bejne/rmO0gK2anZV5p9U

[@aaaab384]

If you have such a thick accent, consider SLOWING DOWN A LOT.

[@einfacherkerl3279]

his talking style is very...... weird