New to kotlin, and I've been trying to figure out what the best practices are for null checks in kot...

# announcements

[Gyuhyeon]

New to kotlin, and I've been trying to figure out what the best practices are for null checks in kotlin. The suggestions are all over the place, and they rarely consider usages other than a single liner.
I'd like some opinions on the following:

if (someObj != null) {
    val someOtherLogic = repository.selectOne(someObj.field)
    someOtherLogic.doThis()
    someOtherLogic.doThat()
} else {
    someService.someBusinessLogic()
}

apparently, checking null with if statements is not the "kotlin way". [citation needed]
from what I've gathered, the "kotlin way" is the following.

someObj?.also {
    val someOtherLogic = repository.selectOne(someObj.field)
    someOtherLogic.doThis()
    someOtherLogic.doThat()
} ?: run {
    someService.someBusinessLogic()
}

but honestly, this looks like some serious code-smell to me. Maybe it's because I come from java, but if what the code is trying to achieve is do some business logic based on the isExists state of an object and do something else if it doesn't exist, using ?.also{} ?: run{} seems way worse than an explicit easy to read if / else.

Any input would be appreciated.

[wasyl]

`if`s are fine, especially in the scenario like yours. It’s only tricky if someObj is a nullable property, in which it will not be smart-cast inside the if block.

[wasyl]

Sometimes ?.let, ?.also etc. will be more readable, but if Kotlin didn’t want us to use `if`s they’d have not included it in the language 😉

[Gyuhyeon]

thanks for the input - I'm guessing you mistyped mutable property as nullable property?

[wasyl]

yes, well it would have to be both nullable and mutable for this to be a problem I think

[ribesg]

Even if it was mutabe & nullable I would prefer to do val someObj = someObj before doing an if rather than the monstruosity that is your second code bloc

[Dico]

I prefer the first as well.

[toffe]

Readability > all (other words: use the if one)

[Stephan Schroeder]

I like this book as a source of Best Practices https://leanpub.com/effectivekotlin