Scala中Clojure的并发原语的真正替代品

Question

In Clojure I have four primitives to manage concurrency scenarios

1. Refs - manage coordinated, synchronous changes to shared state
2. Atoms - manage uncoordinated, synchronous changes to shared state
3. Agents - manage asynchronous changes to shared state
4. Vars - manage thread-local state

My questions is - is there a mature equivalent to each of these in Scala?

Assumptions - I'm going to assume that:

• Actors are a different way to solve the problems that agents do - but they are no means a drop-in replacement
• I'm aware there are agent libraries in Scala - I'm curious to know if they're considered mature

Answer 1

Most of the concurrency constructs you listed for Clojure are based in software transactional memory. Because of that, I think you're basically just asking about STM support in Scala. According to the Akka documentation , the best choice for STM in Scala is ScalaSTM , and they say it's actually going to be included in the Scala Standard Library sometime in the future.

ScalaSTM supports Agents and Refs (which I believe were actually based on the Clojure versions). I think the corollary of an Atom would be the Ref.single type, which is just a ref that you can use outside of an atomic block.

Depending on your use case, a good substitute for var would be Java's ThreadLocal or Scala's DynamicVariable . Use ThreadLocal if all you want is thread-local data, but if you actually need dynamic binding, then I think you need DynamicVariable .