CODEWITHSUNDEEP
kotlinkotlin-extension
SIRS
SIRS

Reputation: 624

Create extension that run a function if object is not null

Can I have kotlin extension function that do something like this:

// extension
inline fun <T : Any> T?.runIfNotNull(function: (T) -> Unit) {
    this?.let { function(it) }
}

// some function
fun doSomething(int: Int){
    // do something
}

// doSomething will be called with maybeNullInt as argument, 
// when maybeNullInt is not null
maybeNullInt?.runIfNotNull { doSomething }

basically, what I want is replace 

maybeNullInt?.let{ doSomething(it) }

with

maybeNullInt?.runIfNotNull { doSomething }

Upvotes: 1

Views: 296

Answers (3)

Alexey Romanov
Alexey Romanov

Reputation: 170805

basically I want to do this maybeNullInt?.runIfNotNull { doSomething }

You already can with ?.let (or ?.run): 

maybeNullInt?.let(::doSomething)

You can't write { doSomething } because it would mean something quite different. See https://kotlinlang.org/docs/reference/reflection.html#callable-references for explanation of the :: syntax.

If you define runIfNotNull you can actually use it without ?:

maybeNullInt.runIfNotNull(::doSomething)

(does nothing if maybeNullInt is null).

Upvotes: 4

Sergio
Sergio

Reputation: 30685

Instead of creating your own extension function you can use let function from Kotlin Standard Library:

maybeNullInt?.let(::doSomething)

:: - in Kotlin we use this operator to reference a function by name.

Upvotes: 5

uaraven
uaraven

Reputation: 1107

Yes you can.

Either use function reference 

maybeNullInt?.runIfNotNull(::doSomething)

or pass a parameter in a lambda

maybeNullInt?.runIfNotNull { doSomething(it) }

Upvotes: 1

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