@thi.ng/atom

@thi.ng/atom

About

Clojure inspired mutable wrappers for (usually) immutable values, with support for watches.

TODO

Installation

yarn add @thi.ng/atom

Usage examples

Atom

import * as atom from "@thi.ng/atom";

const a = new atom.Atom(23);

// obtain value via deref()
a.deref();
// 23

// add watch to observe value changes
a.addWatch("foo", (id, prev, curr) => console.log(`${id}: ${prev} -> ${curr}`));
// true

a.swap((val)=> val + 1);
// foo: 23 -> 24

a.reset(42);
// foo: 24 -> 42

Cursor

// main state
main = new atom.Atom({ a: { b: { c: 23 }, d: { e: 42 } }, f: 66 });

// cursor to `c` value
cursor = new atom.Cursor(main, "a.b.c");
// or
cursor = new atom.Cursor(main, ["a","b","c"]);

// alternatively provide path implicitly via lookup & update functions
// both fns will be called with cursor's parent state
// this allows the cursor implementation to work with any data structure
// as long as the updater DOES NOT mutate in place
cursor = new atom.Cursor(
    main,
    (s) => s.a.b.c,
    (s, x) => ({...s, a: {...s.a, b: {...s.a.b, c: x}}})
);

// add watch just as with Atom
cursor.addWatch("foo", console.log);

cursor.deref()
// 23

cursor.swap(x => x + 1);
// foo 23 24

main.deref()
// { a: 24, b: 42 }

Authors

• Karsten Schmidt

License

© 2018 Karsten Schmidt // Apache Software License 2.0