Kotlin Basics

Kotlin Class Extensions 
 
 Extends the functionality of an existing class 
 
 fun Int.addFive() : Int {
 return this + 5
}
 
 
 Does not actaully change the code of the class 
 Provides a function that can be called on instances of the class 
 
 When are Class Extensions Useful in Ktor? 
 
 To seperate business specific routes and logic from the rest of the routes 
 
 Coroutine Contexts 
 
 DEFAULT: Number of threads = number of CPI cores - use this for calculations or if you are uncertain about which context to use 
 IO: Number of threads = 64 or number of cores (whichever is larger) - use this for rest communication or storing data to a file or database 
 MAIN: Number of threads = 1 - is mainly used in android apps to interact with user interface 
 
 Sample Code: 
 import kotlinx.coroutines.*
import kotlin.random.Random

fun main(args: Array<String>) = runBlocking {
 // 64 Threads in IO
 withContext(Dispatchers.IO) {
 repeat (100_000) { // 100_000 = 100,000
 launch {
 firstcoroutine(it) // 'it' will be the current iteration
 }
 }
 println("End of withContext")
 }
 println("End of main function")
}

suspend fun firstcoroutine(id: Int) {
 delay(Random.nextLong()%2000) // The delay is a random number less than 2 seconds
 println("first $id")
}
 
 Running this code gives an output something like: 
 first 0
first 1
first 2
first 5
first 6
first 7
first 8
first 10
first 9
first 11
first 13
...
 
 Notice how the sequence falls out of order? This is threading and Kotlin coroutines in action.