Being able to do this just dawned on me. :heart:

# announcements

[krtko]

Being able to do this just dawned on me. ❤️

[karelpeeters]

You could also have gone the MutableList: List route.

[Tgo1014]

You could remove the return type from the fun to reduce code even more

[krtko]

@karelpeeters Whats the MutableList route? I'm looking at its code and I don't really get the difference.

[krtko]

Lol I just wanted to be able to share code between a Mutable and Immutable class, which defaults on interfaces allows me to do.

[karelpeeters]

You could create separate interfaces for mutable and immutable parts, where the mutable one extends the immutable one.

[Luke]

on a side note, wouldn't longitude in -180..180 be more idiomatic?

[karelpeeters]

Huh I thought InteliJ had a quickfix for that.

[krtko]

I think the longitude in -180..180 method creates unnecessary objects

[karelpeeters]

It does not, compiler optimizes it away to pretty much the ifs you'd manually write.

[louiscad]

You should use extension functions instead of interface functions with default implementations to make sure there's no accidental override redefining what valid coordinates are. You could also use sealed classes.

[karelpeeters]

Making it a nightmare for Java users.

[gildor]

Whats the MutableList route

Another part of this, that you don’t need immutable implementation, you just create a builder function that return you immutable interface

[gildor]

Something like this:

interface Coordinates {
    val longitude: Double
    val latitude: Double
}

data class MutableCoordinates(
    override val longitude: Double,
    override val latitude: Double
) : Coordinates

fun Coordinates(
    longitude: Double,
    latitude: Double
): Coordinates = MutableCoordinates(
    longitude = longitude,
    latitude = latitude
)

[gildor]

also can add operators for destructuring:

inline operator fun Coordinates.component1() = longitude
inline operator fun Coordinates.component2() = latitude