Is there any way to construct an instance that wil...

# announcements

[robin]

Is there any way to construct an instance that will equal any other object?
This comes close:

val any = object {
    override fun equals(other: Any?) = true
}

but only works when doing any == "Test", not the other way around: "Test" == any. Is there any way to make the latter work?

[mfulton26]

robin: Not from what I can tell. Even if you could, you shouldn't. See https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/equals.html.

[robin]

I know these rules, I wouldn't use this on ordinary objects. I was hoping to create some sort of replacement for true pattern matching, which could work like this:

when(a to b) {
    0 to 0 -> ...
    0 to any -> ...
    any to 0 -> ...
}

[mfulton26]

You can accomplish something similar using `Comparable.compareTo`:

fun main(args: Array<String>) {
    println("Test".compareTo(Anything))
    println(Anything.compareTo("Test"))
}

object Anything : Comparable<Any?> {
    override fun compareTo(other: Any?) = 0
}

fun Any?.compareTo(anything: Anything) = 0

[robin]

That would work generally, but I don't think the when statement uses the Comparable interface, does it?

[mfulton26]

Any reason you aren't using if statements?

if (a == 0 && b == 0) {

    } else if (a == 0) {

    } else if (b == 0) {

    }

[mfulton26]

I suppose this works with when to:

when {
        a == 0 && b == 0 -> ...
        a == 0 -> ...
        b == 0 -> ...
    }

[mfulton26]

Or even:

when (0) {
        a or b -> ...
        a -> ...
        b -> ...
    }

[robin]

Yeah those work, but I was looking for a more concise notation, because those quickly get hard to read with longer variable names and more cases.