item in array or array.contains(item). What made me laugh was <https://stackoverflow.com/questions/...

# getting-started

[Ben Edwards]

item in array or array.contains(item). What made me laugh was https://stackoverflow.com/questions/42234775/kotlin-idiomatic-way-to-check-array-contains-value. The posters seemed to want to find the cleverest, most complex way of doing it rather than answering the question. 'item in array' seems the most elegant but is it idiomatic?

[Joffrey]

I think the accepted answer is pretty reasonable, I don't quite get why this doesn't answer your question.

Basically you can use both depending on how readable you find them. I usually use in inside if conditions because I like how it reads. Sometimes contains might feel more natural if it's at the end of a chain of calls. In other cases, I don't mind, I guess it's opinion based anyway

[Joffrey]

By the way, you might want to ask those in #codingconventions

[ephemient]

item in array is idiomatic

[ephemient]

the use of Array in general is not

[Ben Edwards]

Thanks

[Ben Edwards]

@Joffrey another great channel.

[Ben Edwards]

Think I may have found a case for ArrayList
fun dropLoot(name: String): Boolean {
println("$name will be dropped")
return inventory.removeIf { it.name = name }
}
cant work out how to do this for mutanleListOf

[ephemient]

the Kotlin method is

inventory.removeAll { it.name == name }

removeIf comes from Java

[August Lilleaas]

removeIf seems to work on mutableListOf 🤔

[August Lilleaas]

but it won’t work like written in dropLoot since it mutates the list, and returns a boolean

[Ben Edwards]

Sorry don't quite follow

[August Lilleaas]

I suppose you want == there and not =

[ephemient]

you must have set something up wrong; removeIf is one of the new default methods in Java 8: https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html#removeIf-java.util.function.Predicate-
and as such it is callable on a MutableList as long as you're on JVM

[ephemient]

== vs = would break regardless of `ArrayList`/`MutableList`…

[Ben Edwards]

OK, but removeIf still red. Think I may need to use removeAll, just looking into syntax

[August Lilleaas]

seems to work on my machine at least 🙂

data class Thing(
        val name: String
    )

    val inventory = mutableListOf<Thing>(Thing("foo"), Thing("bar"), Thing("baz"))
    println(inventory) // [Thing(name=foo), Thing(name=bar), Thing(name=baz)]
    inventory.removeIf { it.name == "foo" }
    println(inventory) // [Thing(name=bar), Thing(name=baz)]

[Ben Edwards]

Interesting

[Ben Edwards]

But I can do it with

fun dropLoot(name: String): Boolean {
    println("$name will be dropped")
    return inventory.retainAll { it.name != name }
}

[ephemient]

that may mean you don't have jvmTarget="1.8"

[ephemient]

anyhow, largely irrelevant; just use Kotlin's removeAll or retainAll.

[Ben Edwards]

Thanks, where do I find my jvmTarget? I'm using the latest Android Studio.

[Joffrey]

@Ben Edwards it should be in one of your build.gradle(.kts) files - or nowhere at all, but I think the default is now 1.8 so if you have no such setting you should also have no such problem 😄