Is there any better way to access nullable property?

Question

What is the best way to convert sound.id property from nullable to nonnulable and pass it as param of play method?

class Sound() {
var id: Int? = null
}

val sound = Sound()
...
//smarcat imposible becouse 'sound.id' is mutable property that
//could have changed by this time
if(sound.id != null)
    soundPool.play(sound.id, 1F, 1F, 1, 0, 1F)

//smarcat imposible becouse 'sound.id' is mutable property that
//could have changed by this time
sound.id?.let {
    soundPool.play(sound.id, 1F, 1F, 1, 0, 1F)
}

check: http://stackoverflow.com/questions/34498562/in-kotlin-what-is-the-idiomatic-way-to-deal-with-nullable-values-referencing-o — piotrek1543, Aug 18 '16 at 20:33

score 7 · Accepted Answer · answered Aug 18 '16 at 18:34

7

Use the argument provided by let which will be non-null:

sound.id?.let {
    soundPool.play(it, 1F, 1F, 1, 0, 1F)
}

or

sound.id?.let { id ->
    soundPool.play(id, 1F, 1F, 1, 0, 1F)
}

answered Aug 18 '16 at 18:34

mfulton26

29,956
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rafal · Answer 2 · 2016-08-18T18:47:18.997

0

let{} is the solution here.

Just write it like this:

sound.id?.let {
    soundPool.play(it, 1F, 1F, 1, 0, 1F)
}

--edit--

it is an argument here that is of type Int (not Int?) - thanks @mfulton26 for pointing that out

edited Aug 18 '16 at 18:47

answered Aug 18 '16 at 18:34

rafal

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FYI: In this example, `it` is not a *receiver*. If it were then you would need to use `this` instead of `it`. – mfulton26 Aug 18 '16 at 18:36

Is there any better way to access nullable property?

2 Answers2