CODEWITHSUNDEEP
arrayskotlin
Chris Edgington
Chris Edgington

Reputation: 3236

Comparable arrays in Kotlin

Coming from a Swift world I'm trying to figure out how to use comparable functions like min() or max() on an array of objects. In Swift I would use the comparable protocol - 

class Car: Comparable {
    let year: Int

    static func < (lhs: Car, rhs: Car) -> Bool {
        return lhs.year < rhs.year
    }

    static func == (lhs: Car, rhs: Car) -> Bool {
        return lhs.year == rhs.year
    }
}

But how would you do the same in Kotlin? I've tried this but I'm not sure if it's the right approach, or how I would implement the iterable function -

data class Car(val year: Int): Comparable<Car>, Iterable<Car> {

    override fun compareTo(other: Car) = when {
        this.year < other.year -> -1
        this.year > other.year -> 1
        else -> 0
    }

    override fun iterator(): Iterator<Car> {
        TODO("not implemented")
    }

}

Upvotes: 0

Views: 628

Answers (1)

tynn
tynn

Reputation: 39853

Regarding your implementation there's no issue, but you could make it simpler:

data class Car(val year: Int): Comparable<Car> {
    override fun compareTo(other: Car) = year - other.year
}

You should not implement the Iterable interface, because this would make the Car a kind of a collection.

Running the following example with the given Car implementation

listOf(Car(2004), Car(2007), Car(2001)).run {
    println(this)
    println(min())
    println(max())
    println(sorted())
}

yields the output of 

[Car(year=2004), Car(year=2007), Car(year=2001)]
Car(year=2001)
Car(year=2007)
[Car(year=2001), Car(year=2004), Car(year=2007)]

Upvotes: 1

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