When is .forEach {} preferred, vs java-style for l...

# getting-started

[Jonathan Ellis]

When is .forEach {} preferred, vs java-style for loop? It looks like both get support from the language, e.g. destructuring for loop values

[Francesc]

forEach uses an iterator, so if you care about that (you need your loop to be as performant as possible), then you should use the for loop, otherwise it's a matter of preference.

[ephemient]

IMO: only use forEach when it is meaningfully more useful, e.g.

foo["bar"]?.forEach { ... }

is more work to express with for. but otherwise use for

[ephemient]

it should only use an iterator when

@Ruckus not true; it always uses an iterator because that's resolved before inlining happens. e.g.

for (i in 1..10) {} // compiler optimizes this to an increment
(1..10).forEach {} // constructs range object, iterator, and boxes

[Jonathan Ellis]

TIL, thanks all!

[mkrussel]

For the Kotlin coding conventions.

Prefer using higher-order functions (filter, map etc.) to loops. Exception: `forEach`(prefer using a regular for loop instead, unless the receiver of forEach is nullable or forEach is used as part of a longer call chain).

https://kotlinlang.org/docs/coding-conventions.html#loops