Is this syntax is correct `model let some code run code in c kotlinlang #announcements

Mohamed Ibrahim

06/10/2019, 9:29 AM

Is this syntax is correct,

model?.let{ some code} ?: run { code in case model is null}

06/10/2019, 9:30 AM

syntactically correct but IMO just wrong in terms of style, you probably looking for if/else:

if (model != null) { some code } else { code in case model is null }

06/10/2019, 9:35 AM

@Mohamed Ibrahim when you start using kotlin it can be very tempting to use

let

?:

for cases where `if`/`else` are much better fits

i noticed this with myself and most people i've introduced to the language

Pavlo Liapota

06/10/2019, 9:36 AM

Also there is a slight difference between these two. Using `let`: code in

run

will be executed if

model

is `null`or if

some code

let

null

06/10/2019, 9:38 AM

some code
in
let
will return
null

true, which make it even more confusing

if it really matters I prefer this:

val someResult = if (model != null) { some code } else null
if (someResult == null) {
 //code in case model or result is null
}

but usually try to separate checking for receiver nullability and expression result

Stephan Schroeder

06/10/2019, 10:35 AM

I’m still on the “let for everything”-train 😆

06/10/2019, 3:32 PM

Interesting! I’ve used

let

operator when data could have changed in runtime, and also compiler doesn’t allow to have an

if/else

, so that’d be a good idea IMO, use let operator when an

if/else

is not allowed.

06/10/2019, 3:54 PM

I definitely agree with @Jessie on using

let

to wrap mutable variables. But it’s kind of unclear from the sample whether that’s happening.

06/10/2019, 3:56 PM

to wrap Mutable variables

val immutable = mutable

06/10/2019, 4:03 PM

I hate to have to instantiate a new variable just to do that..

someMutable?.let {
  //lock state and do work
}
/*now I don't have another thing hanging around representing old state*/

06/10/2019, 4:28 PM

It's really depends on case, of course, but usually local variable just more readable and has less nesting