What is the relative performance of a `lateinit var` s `isIn kotlinlang #announcements

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Title

Fudge

11/20/2019, 11:09 AM

What is the relative performance of a `lateinit var`'s

isInitialized

? Is it just checking some flag, or is it some expensive reflective operation, maybe it allocates objects?

diesieben07

11/20/2019, 11:19 AM

It's intrinsified to a simple null check.

lateinit var foo: T

becomes

var foo: T? = null

and

isInitialized

simply checks

foo != null

Fudge

11/20/2019, 11:26 AM

thanks

Paul Woitaschek

11/20/2019, 11:35 AM

For stuff like this just check the bytecode and re-compile it to java if you don't understand bytecode well enough

So if you take this code snippet:

lateinit var variable: String

fun main() {
  val initialized = ::variable.isInitialized
}

yawkat

11/20/2019, 11:38 AM

try this site: https://javap.yawk.at/#aCW3vA/procyon

👌 1

Paul Woitaschek

11/20/2019, 11:38 AM

You can just do it in android studio

Find action -> bytecode

public static final void main() {
      boolean initialized = variable != null;
   }

LeoColman

11/20/2019, 1:16 PM

I'd like to point out that there are very few cases when you should use this. You would probably rather use a nullable type than not knowing if a variable was initialized

➕ 2

Don't make your code go

isInitialized

everywhere, or you'll return to a Java

if not null

boilerplate everywhere

💯 1

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