Unity async / await: Coroutine's Hot Sister [C# & Unity]

The C# async / await workflow can simplify your code and give you more granular control over your game in Unity.
Learn how to convert your current coroutine workflow, what a task is, how to run sequential and synchronous code and how to return data from an asynchronous function.
UniTask: github.com/Cysharp/UniTask (Provides an efficient allocation free async/await integration for Unity)
❤️ Become a Tarobro on Patreon: / tarodev
=========
🔔 SUBSCRIBE: bit.ly/3eqG1Z6
🗨️ DISCORD: / discord
✅ MORE TUTORIALS: / tarodev
0:00 Super professional intro
0:30 Standard coroutine workflow
1:19 Converting to async / await
2:44 Use-cases of async / await
3:10 Running functions sequentially
6:00 Waiting for synchronous tasks to complete
10:20 Mixing sequential and synchronous tasks
11:00 Returning data from an async function
14:20 Calling an async function from a non-async function
15:10 WebGL caveat
15:45 Other advanced async techniques

[@vertxxyz]

There are certainly other important caveats to mention with async. You were constantly getting NREs in the background. This being caused by the fact that tasks do not respect Unity Object lifetimes. Coroutines will stop when the object that started them is destroyed. Tasks will continue on regardless, and this means that they can continue outside of playmode, and through scene changes. To counter this you need to use cancellation tokens, and they're somewhat difficult to grasp. In reality almost every task you start should really take a cancellation token. Not only this, but there are situations you can get yourself into that completely silence exceptions occurring within a task-returning method. If you do not await a task it will not appropriately throw exceptions created within it. This can make bugs difficult to track down, and if you're not familiar with that fact it's a minefield.

[@fahmyeldeeb2542]

Great addition, thank you, I did not know this

[@braniacba6842]

Personal experience, rotating is fine yet setting material property blocks can lead to silence exceptions. Unity really doesn't like having its API called in another thread. I heard that the Unity team is improving the workflow with async/await, but for now, it's causing more pain than it alleviates in most cases.

[@JianqiuChen]

Oh wow, thanks for pointing these out.

[@raii3944]

Indeed, this. async / await workflow is definitely not a coroutine killer. I've spent Last 3 hours tracking down an exception that did not log nor give any hint that there is a problem other than a certain function just not calling. In more complicated scenarios this is would be a pain

[@LagunaCloud]

I think it's a mistake not to bring up async function garbage collection. There's a reason they created a "ValueTask" structure. Especially in game development you have to keep your head on top of the memory allocation and deallocation game. You can quickly start running into garbage collection issues if you're throwing willy nilly async functions everywhere.

[@APaleDot]

I think I ought to mention that most of the advantages listed here in favor of async/await are also present in Coroutines, but he doesn't write the Coroutine version in a way to take advantage of them. For instance, when running Coroutines sequentially, you do not have to make a bunch of different functions and then a separate function to yield on each function sequentially. You can simply do what he does for the async function. You can have that function return IEnumerator (just like how he changes it to async) and run it using StartCoroutine. Then you simply yield return for each shape just like he does with the async version. So in code it looks like this: public IEnumerator BeginTest() { for (var i = 0; i < _shapes.Length; i++) { yield return _shapes[i].RotateForSeconds(1 + i); } } Compare to the async version. It's identical. Similarly, when talking about ways to wait for all the Coroutines to finish he doesn't even mention WaitUntil, or the fact that you can simply yield on Coroutines after starting them. The later method leads to code which is very similar to what he writes for the async function: public IEnumerator BeginTest() { _finishedText.SetActive(false); Coroutine[] tasks = new Coroutine[_shapes.Length]; for (var i = 0; i < _shapes.Length; i++) { tasks[i] = StartCoroutine( _shapes[i].RotateForSeconds(1 + i) ); } foreach (Coroutine task in tasks) yield return task; _finishedText.SetActive(true); } Which again is almost identical to his async version. The major advantage of async functions is the fact that you can return values from them like a Promise in Javascript. But Coroutines are native to Unity and are therefore better integrated into that system: for instance Coroutines line up with the frames of the engine as he mentions, async functions often continue even after you hit stop in the editor which he doesn't mention. Also, some default Unity methods (such as Start) can be converted directly into Coroutines simply by making them return IEnumerator.

[@jerms_mcerms9231]

This is AWESOME! Thank you!

[@diegonorambuena4194]

I didn't see this comment before, but it's a very helpful one. Thanks for showing examples and details of the Coroutines features

[@kdeger]

Perfect use cases, great samples for comparison. Really makes you eager to use Tasks in your code. On point tutorial, good work!

[@Tarodev]

Thanks! I tried to make the (voiced) use cases as practical as possible.

[@YulRun]

I don't like comparing content creators, as everyone has a unique approach. But you're basically the Brakeys 2.0 in the void of Brakeys. GIving us more indepth, higher level tutorials that is exactly what the space needs. You definitely deserve much more Subscribers.

[@Tarodev]

This is truly the highest praise. Thanks Matt.

[@dsbm2153]

I think Brackeys is overrated. He never explained what his code did in particular which made learning difficult and fixing potential issues with the copy-pasted code impossible. Also, copy-pasting code just straight up isn't fun

[@Tarodev]

@@dsbm2153 If you look at some of his older videos you can see he did some pretty complex stuff and covered useful mathematics concepts, which also had deep explanations. Toward the end, I think he just had such a massive new-dev following he just ended up catering to them. I'm trying to avoid going full beginner-friendly by throwing in advanced stuff too.

[@emiel04]

@@Tarodev I love the advanced stuff, content online is almost always beginner level, having these more advanced concepts in a very good format is very nice. Thank you!

[@Cielu1]

@@Tarodev You are doing such a great job on explanation. Niche on more mathematical / advanced concepts. We need it!

[@thinker2273]

Too few developers who learn C# through just Unity understand that using IEnumerable for asynchronicity is not a typical thing in C# and that the purpose of the IEnumerable interface has literally _nothing_ to do with asynchronicity.

[@RogerValor]

true, but it depends on whether you have background in other languages (or even C# itself) or not. For me it was pretty clear that this is just using a general interface in some external task system. I think any Unity dev should learn C# indepently in any circumstance. This isn't so different for any issue where the Unity Engine is your event handler, even MonoBehaviour entrypoints.

[@humadi2001]

Non-boring details from years of experience. I'm surprised of the way you've put all this information together in one video! Thank you!!!

[@NexysStormcloud]

I think it's worth mentioning that async/await continues to work in the editor even after the game has stopped, unless you set an exit condition that takes this into account. Can lead to unexpected results, especially if moving, adding or removing scene objects, playing sound, etc. occurs inside asynchronous functions.

[@CharlieVillalobosDev]

Hey there , I just found your channel. I work full time as a C# backend dev and I always wondered how to apply all of these tools I use all the time like Tasks in Unity. I appreciate you doing these kinds of explanations nobody else on youtube is willing to do. Good work!

[@IvarDaigon]

Quick Tip. don't use async void because because any exceptions can disappear into a black hole. Try to get into the habit using async Task so that you know what the result of the function was (whether it succeeded or failed etc) if you want to be even more fancy you can also return a tuple wrapped in a task so you can return whether the function succeeded and also any other useful info if it failed, this will help when trying to debug the function so that you don't have to step through the entire thing. I like to use this pattern: async Task DoSomething() var result = await DoSomething().ConfigureAwait(false) if (result.success) { //Do another thing after success. } else { //Do something else after fail. Log($"DoSomething() failed because: {reason}"); }

[@Tarodev]

Great suggestion. You can still try/catch a void async method and get it's thrown error, but your technique is great for handled workflow errors.

[@coloneljcd6041]

@@Tarodevthats actually not true, even a try catch wont get the error because its never returned, and it will crash your app

[@thomasloupe]

@@coloneljcd6041 This is correct, any async void exceptions will propagate (bubble) up to the first non-async method, which can oftentimes be your application's entry point.

[@GenSpark1]

Almost spooky how well timed this is, having some trouble with Coroutine Sequentials and cancelling a Coroutine, so this is perfect! Great explanation and well spoken, definite subscribe! :D

[@doismilho]

Finally some quality content for unity devs. I can't take any more "let's make a game from scratch" videos that teach you the very basics. When you get past that, you can't find anything! As an example, I dare you to find a video themed "save/load system in Unity" that will NOT teach you how to read to/write from playerprefs. Seriously? -_- Edit: yes please advanced usages! For instance, how to properly handle canceling async tasks (like when you have a coroutine and the player starts it again but you want to stop it first, I usually save it to a variable when starting, check if null then stop it before starting again; guess you could do the same?)

[@Tarodev]

It seems a lot of people want the advanced version. I better get busy! Glad you like my content, Tom 😊

[@blakehoughton5244]

Yea, you can save tasks as variables to stop or check them. I think you can also use Cancellation Tokens to stop tasks (may be limited to types of tasks).

[@mrslake7096]

I think the beginner stuff gets more views which is why most videos are basic, I don't have any recommendations, but I think books or advanced courses might help you regarding save & load, you can use this free asset: assetstore.unity.com/packages/tools/input-management/save-game-free-gold-update-81519#description ( if you just want something to get the job done ) - also, Sebastian Lague has some advanced tutorial series: kzbin.infofeatured good luck

[@Kalahee]

3600 videos "How to work with Buttons" and none does it properly. Does work, so would simply plugging your ceiling light in the plug outlet, but would be neither a ceiling light, practical, or safe. I'd be fine with "From scratch" if it wasn't just bad programming hygiene with absolute beginner situation that beginners shouldn't listen to because they'll make a mess they can't properly recover from. Sometimes it's not even good for prototyping.

[@Equisdeification]

Once you are into medium/big size projects, no tutorial will help you, most of the systems that they do are pretty basic and don't scale well. The good thing is once you have the need to create those flexible and easy to use systems, you learn way more and way faster! And some of the tutorials that are more complex, they overcomplicated an easy system, most of the save systems I see have several classes and they mix a lot of stuff, while in reality I only need one simple class that is a helper and that's it.

[@vimalnaran2294]

Nice work covering this subject and displaying the mulitple ways async/await can be used. Even a year+ on after the release of your video, its still a gold nugget!

[@caleb6067]

Everything you do, you do well! I am so excited to see your page gaining traction. It is well deserved

[@Tarodev]

Thanks Caleb, I'm excited too! I'm so glad my teachings are helping so many people now 😊

[@kennyRamone]

Dude, this is easily among the best Unity content I've ever seen in youtube and I would DEFINITELY love that more advanced tutorial

[@brianpurdy2966]

Another great video Tarodev! I would love to see where you take a more advanced video on this topic and keep them coming!

[@nilsmuller-cleve6769]

I've referenced this video many times now, as I'm finding more and more use cases for this. Thank you so much for showing this off!

[@francocougo6396]

When I first learned about Coroutines it was ground breaking, the peak of technology for my silly indie brain. Now I'm finding out about async/await/tasks and it's just wonderful. Truly amazing to see how there's always something new to learn.

[@EricYoungVFX]

So glad I found you, amazing tutorials. This will save me lots of headaches.

[@Freaklittleplayer]

Your are an absolute programming beast. I've never seen someone with so good code tutorials. I'm just commenting this here for you to keep up the good work and so that the algorithm rank you better and spread your channel around

[@Th3Shnizz]

Definitely like the workflow of using Tasks instead of coroutines. You have much better control over it and it certainly makes waiting for things to complete a little easier.

[@betinamascenon4675]

Thank you for the great tutorials! Would definitely love to see those advanced tutorials!

[@hegworks]

I really appreciate these concise tutorials. Thank you so much

[@RobertoDeMontecarlo]

Dude, thank you so much. I mean, really! You made a great masterclass of how to use properly Tasks, Async/Await. Now, I truly understand it. No more crappy code anymore.

[@invalid_studio833]

Wow! I didn't know I needed this tutorial. Job well done, thank you.

[@dageddy]

Lovely. I come from a C# async/await web workflow and got into Coroutines when learning Unity. Am keen to refactor some of my code because of your video. Thanks!

[@RichyAsecas]

I think this is the best Unity async/await tutorial I have ever seen. And I can swear I've seen pretty much of those. It would be great to see more advanced stuff delving into async uses in Unity.

[@Tarodev]

I really appreciate it Ricardo. That's pretty high praise

[@soulinekki1130]

Absolutely agree, I'm in awe at how on point is this video. Very clear example in very compact form.

[@nicholassmith1430]

Found this video awhile ago, but I keep coming back because I forget the snytax or where in my code to implement the async or await functions. Thank you so much for this video as it really helped me on my projects and will continue to help me on future Unity projects.

[@Tarodev]

I hope you watch the amazing intro each time

[@gamepass505]

Your videos are very useful, fun to watch, and nicely explained.

[@pocket-logic1154]

Man.. so many light bulb moments with this channel. You have such a great way of explaining things in simple ways that makes them so much easier to follow and understand. I've been chaining Coroutines for.. awhile now. I never knew you could just use Async to do it this way. Hah! Impressive. Cheers ;-)

[@Rubidev]

As you yourself said, yes, "Beautiful".

[@Maxx__________]

Fantastic video. I've always loathed using coroutines. Thank you!!

[@SirRelith]

I love your super professional intro. :D

[@JimPlaysGames]

Holy crap this is amazing. I had no idea this was a thing and I am definitely putting this to use. Thank you!

[@cahydra]

Thanks for enlightening me about async & await, this will come to great use.

[@pixeldevlog]

Perfect video, loved it and subscribed. I'd love to see more of these videos.

[@roygatz1037]

For newbie Unity C# community, can't be without you

[@DynastySheep]

This is a nice tutorial, I have been using coroutines all the time and will surely start using the async/await in my future projects. Thanks :)

[@djdavidj]

Thank you. I’ve been in Coroutine hell for a few days, this will work for exactly what I need. I think I can replace all my Coroutines with this. Again, thank you!

[@kubstoff1418]

this is my first vid from you I've watched, but after 4 mins I subscribed instantly, such clear message and comprehensive explanation!

[@Tarodev]

Thank you so much! Glad to have you on board

[@vincentlauwen9742]

You opened my eyes. Great vid!

[@Storymen12369]

This is exactly what I was looking for. I love this video.

[@dr.angerous]

Wow. Just wow. I wish every tutorial was just like this

[@tailwindmechanics7454]

This was awesome, would definitely love a deeper dive into this

[@frazoni.]

This is also super useful for loading levels asynchronously

[@fernandoferreira5156]

never stop making content, thank you

[@sickboi11111]

This was so handy, saved me a bunch of headscratching, thanks!

[@SpicyMelonYT]

This is so great. I use async and await for JavaScript stuff, I had no idea C# had this. I LOVE IT!

[@kingreinhold9905]

Subscribed! You really opened a whole new world to me...

[@ckwallace]

coming from a javascript background and being familiar with Promises (and having trouble wrapping my mind around coroutines) this video is a lifesaver! thank you so much

[@Tarodev]

And lucky for you, unity is focusing heavily on improving async work flows. Major updates coming soon!

[@TheXentios]

This is amazing info for 16 minutes. Well done. Also thanks for the Webgl warning.

[@epiphanyatnight8732]

This just taught me how async works finally. Thanks a ton!

[@thorbrigsted5580]

Great guide. Covers all the points i was interested in

[@LiquidMark]

I never knew about async, thank you for the informative video!

[@_g_r_m_]

Great introduction! I've never heard of it and would love to learn about more advanced stuff.

[@yvanrichani7631]

This is an extremely useful video, thank you!

[@Selconag]

That was my first time I easily used a hard topic, thank you. I will tell everybody how you meme'd a really good topic(Of course usage too). I will watch every use case video you will release. Hope there will be more meme intros too.

[@rem3072]

Video made me subscribe ! Great channel mate

[@gastonclaret2012]

Great tutorial, thanks for this

[@bloom945]

WHAT. thats so op????? just found your channel, great stuff

[@stressbuster5500]

super professional intro lol Easy to understand with indepth details as all your videos. Keep making such videos thanks

[@Tarodev]

Not sure what I was thinking with that intro...

[@joakin8535]

This is it man. Quality content!

[@OmegaFalcon]

This was incredibly useful. Exactly what I needed rn

[@Tarodev]

Take this tool and grow strong my child

[@antonkorshunov4979]

Just a great and enough deep explanation, rewatched it several times). Thanks

[@ultramelon3960]

I will definitely have to keep this one in mind! 👍

[@zekiozdemir420]

Thank you! needed this

[@path1024]

Oh... my... god. I've been self-taught for 42 years (since I was 7). I picked up C# about 17 years ago. I had NO IDEA you could do this. I have my own class for things that are timed. I never watched videos until I started with Unity and I'm learning SO MUCH even after all this time about programming in general. This is CRAZY POWERFUL and I bet every mid-level coder knows about it. I remember a few years back when I learned about reflection and params. That blew me away. I have had the ability to do basically what NetCode does for quite a while: have the server call a function on the client or visa versa.

[@Tarodev]

I'm honoured I could show you something new after 42 years. I hope it makes your programming life even better going forward 😊

[@path1024]

@@Tarodev I fall asleep reading books. I've learned by running into specific issues and then solving them. I can be extremely creative, but I bet you have me beat technically. Even a short time exposed to a professional environment would be very valuable. For whatever reason I've taken to watching Unity videos like I never did with my 2D projects and my knowledge is absolutely exploding. It's strange to have so much experience and then be exposed to even basic things that I simply didn't know existed. I feel like I'm about to take my ultimate form. Thanks for the great videos. =)

[@Tarodev]

@@path1024 you'd be surprised. I've done no formal (paid) training and have never even completed a full programming course. I also have learned by doing. Looking things up as I go. It's worked well for me so far and keeps things I learn very specific to my workload.

[@path1024]

@@Tarodev It's because I simply haven't sought out information. I only looked for what I needed to accomplish the task. Your videos show a knack for determining what I need to know and didn't know I needed to know it. Imagine being a native English speaker, and a creative one at that, but living 49 years in a hypothetical location with a limited vocabulary. Then you move to Sydney or New York. You grasp new words instantly and can see their full power and use right away because you're a native speaker. That's what this is like. I'm about to become the Hemingway of coding.

[@mooumari8210]

Amazing tutorial, well explained

[@svendpai]

Amazing stuff!

[@deivid-01]

Great explanation! Keep the great work up!

[@igz]

Nice one, would love to see a more advanced workflow, especially on how to deal with canceling tasks. The thing I still like about coroutines is that it kills itself when the game object is destroyed. With async/await (in my experience) it tends to get very complex with cancellation tokens and all of the try/catches everywhere.

[@Tarodev]

I really should have mentioned this issue. I was planning to and somehow just forgot. I'll include cancellation tokens in the next one 👍

[@IvarDaigon]

you can have a cancellation token baked into the object so that when it is disposed it cancels all running tasks associated with that object. You generally only need to use cancellation tokens with long running tasks anyways, because short ones will just exit on their own.

[@schnips9142]

From now on, I'll no longer say "he's suicidal" but "he identifies as a Coroutine".

[@mikeken7105]

@@Tarodev I would like to know if the next section has been updated? Where can I find it? Thank you.😀

[@Izzy-fr1zu]

@@Tarodev Did you make a second video on the topic? I couldn't find one on your page, but maybe I missed it? I would be very interessted in a workflow for parallel loops!

[@ZuloYT]

love the examples, awesome video! well described!

[@lordhitnrun4335]

love your content !

[@brkhnzn]

So helpful before my exam. Thank you so much.

[@narkopraxis602]

Awesome video! A great way to start my day!

[@sadparad1se]

Cool! Nicely explained.

[@utkuerden6269]

Great video totally and look forward to advanced tutorial

[@olon1993]

This was a great intro. Would love a deeper dive!

[@narkid89]

Absolutely awesme video, consise and clear with great examples. You've got a new subscriber! ^^

[@Tarodev]

Thanks Dikran!

[@sly1cooper]

Thanks for the easy explanation :)

[@richardbeare11]

Would love to see that more advanced async workflow tutorial that you alluded to! You do a great job here.

[@jean-michel.houbre]

Awesome tool! Thanks.

[@Mrawesome1908]

What a great tutorial that I didn't even know I needed :3

[@Tarodev]

Go live your best async life

[@BeeGameDev]

This is great. Thanks for sharing.

[@DanPos]

Awesome video Tarodev - will definitely be using async more often now!

[@Tarodev]

You look to have some interesting tutorials on your channel! I'll sub and take a peak shortly

[@DanPos]

@@Tarodev Thanks a lot!

[@vrtech473]

Advance tutorial workflow for async is a MUST ! :D

[@majeddev]

Yes an advanced one would be nice. Great tutorial btw!

[@dfadir]

Quality stuff, man! Keep it up

[@Tarodev]

I'll do my best 🤪

[@rickyspanish4792]

Wow! That super professional intro

[@Tarodev]

Lol... yeah. Not sure what I was thinking

[@hermanusjohannesbesselaar2499]

Just blew my mind. Thanks this will already save me so much trouble. Can't wait 😉 to watch the awaitable video next! Thanks a lot for this, Definitely getting my like!

[@Sonic-ig1po]

Please read the first couple of comments, what this guy is doing is irresponsible generally and will hurt your code without a proper understanding of what is happening. No insult intended just a want to save you from untraceable errors.

[@hermanusjohannesbesselaar2499]

@@Sonic-ig1po Thanks for taking the time to warn me about this. I will definitely look it some more. I started out using coroutines but thought the async await looked a lot cleaner. Just reading the comments is a scary education in itself.

[@ViniciusNegrao_]

Async/await is kinda like second nature for people who know ES6, where before we had to pass a callback function as a parameter, now we can simply call await for asynchronous functions. It's great to know this feature exists in C# and it really helps that you can control how they flow, having dependent coroutines running would be a nightmare and some sort of semaphore would have to be used

[@balasubramanimudaliar1336]

great tut😀

[@libberator5891]

Another banger! This man just poops out quality content

[@Megarith1to3]

Gotta admit, when I tried this after Coroutines failed me, I didn't think it'd work. But it did after minimal tweaking. I'm impressed. For reference, I am currently doing the Unity Junior Programmer pathway, so very very new to this. Thank you for explaining this so well. Some went over my head, but I reckon I'll learn with time.

[@chicao.do.blender]

amazing stuff

[@mikrokaulis32k68]

Clean video. Thanks a lot didnt know this thing even existed less go

[@NITIN-ll4un]

Very helpful .... ❤️

[@user-xo1uy3wt4l]

It's Perfect Tutorial!!!! Thank you~

[@Tarodev]

Yay!!

[@NewtonJR1987]

Great video, thanks!

[@Tarodev]

Glad you liked it!

[@Ali_khalaj]

i wish you make more advanced tutorials about asyncs

[@mov4736]

Thanks! Pretty good video!