How would I fix this code I d like `reportError ` to be call kotlinlang #announcements

Ellen Spertus

11/07/2019, 8:20 PM

How would I fix this code? I’d like

reportError()

to be called if the value preceding

let

store.state.selectedTab?.content?.url.let {
     doSomething(it)
 } ?: run {
     reportError("Unable to get URL to send")
 }

Assume that both

doSomething()

reportError()

11/07/2019, 8:21 PM

if you don’t need to capture that

url

, why not just use if/else?

Ellen Spertus

11/07/2019, 8:21 PM

Oops, I oversimplified my code. I have edited it to add

it

Anastasia Finogenova

11/07/2019, 8:22 PM

This code will not compile if url is nullable

Ellen Spertus

11/07/2019, 8:22 PM

url

isn’t nullable, but

selectedTab

content

11/07/2019, 8:22 PM

I think you want

?.let

11/07/2019, 8:23 PM

Anastasia Finogenova

11/07/2019, 8:23 PM

If you don't do ?.let it will not compile

11/07/2019, 8:23 PM

but also, still, if/else would work just fine here

Ellen Spertus

11/07/2019, 8:23 PM

Thanks, @Luke. Could you explain why?

@Shawn Wouldn’t I have to save the argument to

doSomething()

11/07/2019, 8:24 PM

you would, but imo that’s not such a big deal

also, the result of a safe-navigation call is always nullable, so you’ll need to keep using

?.

as you navigate through the structure

11/07/2019, 8:25 PM

let

is callable on nullables.

store.state.selectedTab?.content?.url

returns null if any call return null, in which case

it

is null inside

let{}

run

is never called

by adding ? before

let

, you don’t call it if no url can be found

Ellen Spertus

11/07/2019, 8:26 PM

Thanks, @Luke.

11/07/2019, 9:02 PM

What's wrong with just doing

val url = store.state.slectedTab?. content?.url
if (url != null) doSomething(url) 
else reportError...

11/08/2019, 12:42 AM

when(val url = store.state.slectedTab?. content?.url){
    null ->reportError()
    else -> doSomething(url) 
}

Stephan Schroeder

11/08/2019, 10:02 AM

@Kroppeb nice work! the format looks cleaner to me (a happy coincidence that

null ->

else ->