Bottom Up View of Coroutines Rooparsh Kalia SDE 2 at Mutual Mobile @i_am_rooparsh

Synchronous way

UI blocking BLOCKS THE MAIN THREAD

Asynchronous way

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CALLBACK HELL

Callback Hell A callback is a function that will be executed after another function has finished executing. And if there are a series of things to be done synchronously then we will fall into callback hell that can lead us to ambiguity in understanding the code. It depends on the number of steps and logic we have in our applications

RxJava/RxKotlin We can also opt for RxX stack from Reactive world, but that mean we are required to add another tool in our knowledge domain as well as our project.

Some issues with Rx : 1. Learning curve 2. Project level structural changes 3. Dependency on 3rd Party.

Combine the best of 2 worlds Async + Sync = Coroutines

Why I love Coroutines? ❤ Asynchronicity expressed as sequential code that is easy to read and reason about!

What are Coroutines? Coroutines are nothing but light-weight threads. Coroutines provide us an easy way to do synchronous and asynchronous programming.

From Official docs, “One can think of a coroutine as a light-weight thread. Like threads, coroutines can run in parallel, wait for each other and communicate. The biggest difference is that coroutines are very cheap, almost free: we can create thousands of them, and pay very little in terms of performance. True threads, on the other hand, are expensive to start and keep around. A thousand threads can be a serious challenge for a modern machine.”

Sample code for coroutine

Sample code for coroutine Blocking Code

Suspend behind the scenes

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Coroutine Basic Terminology 1. Dispatchers 2. CoroutineContext 3. Job 4. CoroutineScope

1. Dispatchers 2. CoroutineContext 3. Job 4. CoroutineScope Determines what thread or threads the corresponding coroutine uses for its execution. The coroutine dispatcher can confine coroutine execution to a specific thread, dispatch it to a thread pool, or let it run unconfined.

1. Dispatchers 2. CoroutineContext 3. Job 4. CoroutineScope ● Dispatchers.IO ● Dispatchers.Main ● Dispatchers.Default

1. Dispatchers 2. CoroutineContext 3. Job 4. CoroutineScope Coroutines always execute in some context represented by a value of the CoroutineContext type, defined in the Kotlin standard library.

1. Dispatchers 2. CoroutineContext 3. Job 4. CoroutineScope Coroutine Task

1. Dispatchers 2. CoroutineContext 3. Job 4. CoroutineScope The scope in which the job will run.

Coroutines in work

Coroutine Scope

Coroutine Scope In android, we have : ● viewModelScope ● lifeCycleScope

Coroutine Scope In android, we have : ● viewModelScope ● lifeCycleScope

Coroutine Scope In android, we have : ● viewModelScope ● lifeCycleScope

Coroutine Scope

Coroutine Context A coroutine context is an indexed set of elements that define the behaviour of a Coroutine.

Coroutine Context ● CoroutineDispatcher ○ Dispatchers.IO ○ Dispatchers.Default ○ Dispatchers.Main ● CoroutineExceptionHandler ● CoroutineName ● Job

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Some Use cases of Coroutine: 1. Parallel/Series Network Call 2. Handling Exceptions 3. Managing Thread for Disk operations

Practical Time

Difference between launch and async The difference is that launch returns a Job and does not carry any resulting value, while async returns a Deferred -- a light-weight non-blocking future that represents a promise to provide a result later. So async starts a background thread, does something, and returns a token immediately as Deferred .

Coroutine Advanced Jobs : Supervisor Jobs, Child Jobs. Continuation Cancelling Job

QnA Time Any questions ?? Feel free to drop any queries and follow me at @i_am_rooparsh