Hmm - i m still unsure of how coroutines will be u...

# coroutines

[asad.awadia]

Hmm - i m still unsure of how coroutines will be used in real life situations.. other than syntactic sugar to avoid call back hell - is there anything it provides?

[louiscad]

Can be used for async I/O, can be used to await events like the code was blocking a thread, but without blocking a thread. I see plenty of usages where doing so without coroutines would require a callback hell if even possible. I personally use coroutines for Bluetooth Low Energy connections: https://github.com/Beepiz/BleGattCoroutines

[asad.awadia]

can be used to await events like the code was blocking a thread, but without blocking a thread <--- this is exactly what I thought they provided too - do u have any examples?

[hiperbou]

I use coroutines to encapsulate and to have a clean and common way to use all the async functions of third party libraries, for example.. some lib uses promises -> coroutine, other uses callbacks -> coroutine, other signals -> coroutine.. keeps my code clean and readable..

[louiscad]

@asad.awadia Let's say you want to await an internet connection before attempting your network call. You could write a function that would suspend until there's an internet connection. Then, you would call awaitInternetConnection() in a coroutine (a suspend block), and your code would go past the awaitInternetConnection() call only when the internet connection is there, that is, when the method resumes from suspension, and would do this, without blocking any thread or locking up precious ressources

[louiscad]

@asad.awadia Such behavior can implemented in different ways. I made a similar thing that suspends until a Bluetooth Low Energy connection is performed, which relies on this Gate class: https://github.com/Beepiz/BleGattCoroutines/blob/bdb7b82b2b46f813633ae471122c19754aab939c/blegattcoroutines/src/main/java/com/beepiz/bluetooth/gattcoroutines/experimental/Gate.kt

[asad.awadia]

is awaitInternetConnection() a suspend function or is it of the form fun awaitInternatConnection() = launch {//code}

[asad.awadia]

but if i call it in a runBlocking it will block the thread which voids the whole point correct?

[louiscad]

It can only work if awaitInternetConnection() is a suspend function

[asad.awadia]

but what if the code inside the awaitInternetConnection is blocking?

[asad.awadia]

the suspend doesn't do anything right --- the code inside needs to be non blocking in the first place

[louiscad]

runBlocking blocks the thread, making it available solely for the coroutine inside the block. It is useful on JVM (not Android) to avoid the main thread to terminate, and allows to use it in a coroutines context

[louiscad]

What blocking code are you expecting in an awaitInternetConnection() function?

[asad.awadia]

wouldn't waiting for a connection inherently be blocking?

[louiscad]

What I call blocking code is code that does synchronous I/O or significant computations. CPU computations should be done in CommonPool most of the time. Blocking I/O should be done on a thread pool properly sized for the running environment (like you'd do in Java), but for prototyping, having a global (top-level) val IO = CommonPool is okay as long as it doesn't locks up CPU-bound computations that are normally the stuff CommonPool is made for.

[louiscad]

You then use CommonPool, IO or other coroutine contexts as arguments for async(...) { ... } and launch(...) { ... }

[louiscad]

And no, waiting for an internet connection is not inherently blocking. In Android for example, you get a callback in a BroadcastReceiver when connectivity changes, where you can check again if the active connection (if any) is connected to internet. You could then feed this to a BroadcastChannel consumed by various parts of your program, or feed it to a class like the Gate class I showed you earlier, that could the be used to write a suspending awaitInternetConnection() suspend function