Managing State with Atoms

An atom is a reference to an immutable value. The value can change over time, but each change is an atomic “swap to a new value.”

The most important habit is: update an atom by providing a pure function.

1(def counter (atom 0))
2
3(swap! counter inc)   ;; => 1
4@counter              ;; => 1

Under the hood, swap! is CAS-style: if another thread updates the atom concurrently, Clojure retries your function with the new value. That is why the function must be free of side effects.

Java mental model: atom updates are like AtomicInteger.updateAndGet, but generalized to any value (often a map).

In this section

• Mastering State Management in Clojure: Creating and Using Atoms
  Learn how to effectively manage state in Clojure using atoms, a fundamental concurrency primitive. Explore creation, usage, and best practices for atoms in functional programming.
• Atom State Management in Clojure: Mastering `swap!` and `reset!`
  Explore how to manage state in Clojure using atoms, focusing on the `swap!` and `reset!` functions. Learn how these functions ensure atomic updates and handle contention, with practical examples and comparisons to Java.
• Practical Scenarios for Atoms: State Management in Clojure
  Explore practical use cases for Clojure atoms, including counters, caches, and configuration management. Learn when to use atoms for independent state changes.