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How to cache the results in scala?

 2 years ago
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How to cache the results in scala?

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This page has a description of Map's getOrElseUpdate usage method:

object WithCache{
  val cacheFun1 = collection.mutable.Map[Int, Int]()
  def fun1(i:Int) = i*i
  def catchedFun1(i:Int) = cacheFun1.getOrElseUpdate(i, fun1(i))
}

So you can use catchedFun1 which will check if cacheFun1 contains key and return value associated with it. Otherwise, it will invoke fun1, then cache fun1's result in cacheFun1, then return fun1's result.

I can see one potential danger - cacheFun1 can became to large. So cacheFun1 must be cleaned somehow by garbage collector?

P.S. What about scala.collection.mutable.WeakHashMap and java.lang.ref.* ?

See the Memo pattern and the Scalaz implementation of said paper.

Also check out a STM implementation such as Akka.

Not that this is only local caching so you might want to lookinto a distributed cache or STM such as CCSTM, Terracotta or Hazelcast

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