I have a float I want to pass around that should always be in a given range (0.0f.1.0f) I don't want...

# random

[Fergus Hewson]

I have a float I want to pass around that should always be in a given range (0.0f.1.0f) I don't want to write asserts for it at every level of my app, only at I/O, how would you represent this?

[Fergus Hewson]

Is this a good idea

@JvmInline
value class Volume(val value: Float){
    init {
        assert(value in 0.0..1.0) {
            "Invalid volume: $value"
        }
    }
}

[romainguy]

Yes

[Fergus Hewson]

When writing tests for below, I get

Cannot invoke "kotlin.ranges.ClosedFloatingPointRange.contains(java.lang.Comparable)" because "Volume.volumeRange" is null

Any idea why?

@JvmInline
value class Volume(val value: Float) {
    init {
        assert(value in volumeRange) {
            "Invalid volume: $value"
        }
    }

    companion object {
        val default = Volume(DEFAULT_VOLUME)
        val volumeRange = 0.0..1.0
    }
}

[darkmoon_uk]

This is an initialisation order problem.
Swap the order of default and volumeRange in the Companion object.

[Adam S]

or wrap Volume(DEFAULT_VOLUME) with by lazy {}

[Piotr Krzemiński]

I wish the order was checked by the compiler, it's confusing to get the error as late as in runtime

[Piotr Krzemiński]

I recall KT-46771 and KT-25796 but both are resolved - is there one for the JVM?