惯用的 Scala Map upsert
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Idiomatic Scala Map upsert
提问by Dave Ray
I'm working with a map in Scala and doing the usual "if there's no value associated with a key, create it, put it in the map and return it":
我正在 Scala 中使用地图并执行通常的“如果没有与键关联的值，则创建它，将其放入地图并返回它”：
def alphaMemory(key : AlphaMemoryKey) = {
var am = map.getOrElse(key, null)
if(am == null) {
am = new AlphaMemory(key)
map.put(key, am)
}
am
}
To me, this does not feel like idiomatic Scala code. It feels like Java. Is there a more succinct way of writing this? It looked like maybe I could override Map.default() to insert the new value and return it. Not sure though.
对我来说，这不像是惯用的 Scala 代码。感觉像Java。有没有更简洁的写法？看起来也许我可以覆盖 Map.default() 以插入新值并返回它。虽然不确定。
Thanks!
谢谢！
回答by sblundy
mutable.Maphas V):V" rel="noreferrer">getOrElseUpdatewhich does exactly what you want, no idiom necessary.
mutable.Maphas V):V" rel="noreferrer">getOrElseUpdatewhich 正是你想要的，不需要成语。
