I have a `values: mutableMapOf<String, List<...

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[Ellen Spertus]

I have a values: mutableMapOf<String, List<String>. Is there a better way of adding items to it than:

values[key] = (values[key] ?: emptyList()) + value

My API level is to low for getOrDefault().

[deactivateduser]

That looks ok to me. Expressive enough to understand.

[Ellen Spertus]

Thanks, although it seems like there should be a nicer way. I’m writing an extension function…

[Ellen Spertus]

fun MutableMap<String, MutableList<String>>.add(key: String, value: String) =
    this[key]?.run {
        add(value)
    } ?: set(key, mutableListOf(value))

[Marc Knaup]

I use that pattern quote often:

val values = mutableMapOf<String, MutableList<String>>()

fun add(key: String, value: String) {
    values.getOrPut(key) { mutableListOf() }.add(value)
}