Watch a single property without "auto"

Is there a way to apply watch just to specific object key rather than the whole object? I have a large observable state, and need to trigger some side effect when certain properties change. The side effect doesn’t use the object I’m watching so I can’t use auto, and watch on the whole state will cause the side effect to fire unnecessarily.

A simple example below, is it possible to log "side effect" to the console when count changes but not when number changes? https://codesandbox.io/s/serene-frog-5uige

const state = o({
  count: 0,
  number: 0
});
watch(state.count, () => console.log("unrelated side effect"));

function App() {
  return (
    <div className="App">
      <button onClick={() => state.count++}>Count ++</button>
      <button onClick={() => state.number--}>Number --</button>
    </div>
  );
}

EDIT: Perhaps the best way is to just to reference the value in auto and never use it?

auto(() => {
  const watch = state.count;
  console.log("unrelated side effect")
})

[aleclarson]

You can now use watch to observe a single property. Just note that if the property points to an observable object, that entire object will also be observed.

import { watch } from 'wana'

const watcher = watch(state, 'count', change => {
  console.log('new count:', change.value)
})

watcher.dispose()

[ryanking1809]

Oh I meant an array of properties to react to. eg. (perhaps a better api)

const state = o({ count: 0, foo: 0, bar: 0 })
const observer = onChange([[state, 'foo'], [state, 'bar']], change => {
  // Nothing is ever observed in here.
})