MoraSoftware.github.io/coroutine.html at master · MoraSoftware/MoraSoftware.github.io · GitHub

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<!DOCTYPE html>
<html lang="en">
   <head>
      <title>Class Kotlin</title>
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         </div>
         <div class="block">
            <h2>COROUTINES</h2>
         </div>
         <ul class="nav nav-tabs">
            <li class="active"><a data-toggle="tab" href="#init">Scope</a></li>
            <li><a data-toggle="tab" href="#builders">Builders</a></li>
            <li><a data-toggle="tab" href="#dispatchers">Dispatchers</a></li>
            <li><a data-toggle="tab" href="#code">Code</a></li>
         </ul>
         <div class="tab-content">
            <div id="init" class="tab-pane fade in active">
              <h3>CoroutineScope</h3>
              <p></p>
              <p>Allows objects to provide scope for coroutines </p>
              <p>async & launch become instance methods</p>
              <p>they provide a default context</p>
              <p>To start coroutine scope you can:</p>
              <p>Use GlobalScope that has empty coroutine context.</p>
              <p>Implement CoroutineScope interface. Create a scope from a context:</p>
              <xmp>with(CoroutineScope(context = context)){}))</xmp>
              <p></p>
              <p></p>
              <ul class="list-inline">
                <li>
                <a href="https://blog.kotlin-academy.com/kotlin-coroutines-cheat-sheet-8cf1e284dc35">Reference</a></li>
                <li>
                  <a href="https://github.com/googlecodelabs/kotlin-coroutines">GitHub Google Codelabs</a>
                </li>
                <li>
                  <a href="https://www.youtube.com/watch?v=jYuK1qzFrJg"><img src="static/youtube.png"></a>
                </li>
                <li>
                  <a href="https://www.youtube.com/watch?v=EOjq4OIWKqM"><img src="static/youtube.png"></a>
                </li>
              </ul>
            </div>
            <div id="builders" class="tab-pane fade">
              <h3>Coroutine builders</h3>
              <p></p>
              <p> - launch</p>
              <p>Launches new coroutine without blocking current thread and returns a reference to </p>
              <p> the coroutine as a Job.</p>
              <p>(launch is when you want to fire and forget)</p>
              <p></p>
              <p> - runBlocking</p>
              <p>Runs new coroutine and blocks current theread interruptible until its completion.</p>
              <p></p>
              <p> - async</p>
              <p>Creates new coroutine and returns its future result as an implementation of Deferred.</p>
              <p>async doesn't throw until await() o join()</p>
              <p>(async is when we wnat to run something, then await the resul)</p>
              <p></p>
              <p> - withContext</p>
              <p>Change a coroutine context for some block.</p>
              <p></p>
              <p></p>
              <a href="https://blog.kotlin-academy.com/kotlin-coroutines-cheat-sheet-8cf1e284dc35">Reference</a>
               <a href="https://www.youtube.com/watch?v=jYuK1qzFrJg"><img src="static/youtube.png"></a>
               <a href="https://www.youtube.com/watch?v=EOjq4OIWKqM"><img src="static/youtube.png"></a>
            </div>
            <div id="dispatchers" class="tab-pane fade">
              <h3>Coroutine dispatchers</h3>
              <p>The things wihich runs and schedules coroutines</p>
              <p></p>
              <p> - Dispatchers.Default</p>
              <p>Different thread(if possible) it is backerd by a shared pool of threads on JVM.</p>
              <p>Uses cpuCount threads(core)</p>
              <p>Elastic thread executor</p>
              <p>Default dispatcher</p>
              <p></p>
              <p> - Dispatchers.Main</p>
              <p>Platform specific main thread (if exists).</p>
              <p>Allows running coroutines on UI main thread</p>
              <p></p>
              <p> - Dispatchers.IO</p>
              <p>Thread designed for offloadin blocking IO tasks to a shared pool of threads.</p>
              <p>IO dispatcher uses Dispatchers.Default</p>
              <p>Designed for blocking I/O tasks</p>
              <p></p>
              <p> - Dispatchers.Unconfined</p>
              <p>Always uses first available thread (most performant dispatcher).</p>
              <p></p>
              <p> - newSingleThreadContext</p>
              <p>Creates a new coroutine execution context using a single thread with built-in yield support</p>
              <p></p>
              <p></p>
              <a href="https://blog.kotlin-academy.com/kotlin-coroutines-cheat-sheet-8cf1e284dc35">Reference</a>
              <a href="https://proandroiddev.com/demystifying-coroutinecontext-1ce5b68407ad">Reference</a>
               <a href="https://www.youtube.com/watch?v=jYuK1qzFrJg"><img src="static/youtube.png"></a>
               <a href="https://www.youtube.com/watch?v=EOjq4OIWKqM"><img src="static/youtube.png"></a>
            </div>
            <div id="code" class="tab-pane fade">
              <h3>Resume with code</h3>
              <xmp>
                  import kotlinx.coroutines.*
                  import java.util.concurrent.ExecutorService
                  import java.util.concurrent.Executors

                  fun main(args: Array<String>) {
                      exampleWithContext()
                  }

                  suspend fun printlnDelayed(message: String) {
                      // Complex calculation
                      delay(1000)
                      println(message)
                  }

                  suspend fun calculateHardThings(startNum: Int): Int {
                      delay(1000)
                      return startNum * 10
                  }

                  fun exampleBlocking() = runBlocking {
                      println("one")
                      printlnDelayed("two")
                      println("three")
                  }

                  // Running on another thread but still blocking the main thread
                  fun exampleBlockingDispatcher(){
                      runBlocking(Dispatchers.Default) {
                          println("one - from thread ${Thread.currentThread().name}")
                          printlnDelayed("two - from thread ${Thread.currentThread().name}")
                      }
                      // Outside of runBlocking to show that it's running in the blocked main thread
                      println("three - from thread ${Thread.currentThread().name}")
                      // It still runs only after the runBlocking is fully executed.
                  }

                  fun exampleLaunchGlobal() = runBlocking {
                      println("one - from thread ${Thread.currentThread().name}")

                      GlobalScope.launch {
                          printlnDelayed("two - from thread ${Thread.currentThread().name}")
                      }

                      println("three - from thread ${Thread.currentThread().name}")
                      delay(3000)
                  }

                  fun exampleLaunchGlobalWaiting() = runBlocking {
                      println("one - from thread ${Thread.currentThread().name}")

                      val job = GlobalScope.launch {
                          printlnDelayed("two - from thread ${Thread.currentThread().name}")
                      }

                      println("three - from thread ${Thread.currentThread().name}")
                      job.join()
                  }

                  fun exampleLaunchCoroutineScope() = runBlocking {
                      println("one - from thread ${Thread.currentThread().name}")

                      val customDispatcher = Executors.newFixedThreadPool(2).asCoroutineDispatcher()

                      launch(customDispatcher) {
                          printlnDelayed("two - from thread ${Thread.currentThread().name}")
                      }

                      println("three - from thread ${Thread.currentThread().name}")

                      (customDispatcher.executor as ExecutorService).shutdown()
                  }

                  fun exampleAsyncAwait() = runBlocking {
                      val startTime = System.currentTimeMillis()

                      val deferred1 = async { calculateHardThings(10) }
                      val deferred2 = async { calculateHardThings(20) }
                      val deferred3 = async { calculateHardThings(30) }

                      val sum = deferred1.await() + deferred2.await() + deferred3.await()
                      println("async/await result = $sum")

                      val endTime = System.currentTimeMillis()
                      println("Time taken: ${endTime - startTime}")
                  }

                  fun exampleWithContext() = runBlocking {
                      val startTime = System.currentTimeMillis()

                      val result1 = withContext(Dispatchers.Default) { calculateHardThings(10) }
                      val result2 = withContext(Dispatchers.Default) { calculateHardThings(20) }
                      val result3 = withContext(Dispatchers.Default) { calculateHardThings(30) }

                      val sum = result1 + result2 + result3
                      println("async/await result = $sum")

                      val endTime = System.currentTimeMillis()
                     println("Time taken: ${endTime - startTime}")
                  }
              </xmp>
               <a href="https://www.youtube.com/watch?v=jYuK1qzFrJg"><img src="static/youtube.png"></a>
            </div>
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