Offer utility for state subscriptions, i.e. when a selector's value changes

[devinivy]

No description provided.

[wswoodruff]

Are we imagining a callback similar to store.subscribe?

Howbout an interface like this?

subscribeSelector(M.selectors.something, (newSelectorVal) => console.log('newSelectorVal', newSelectorVal));

[devinivy]

I think something like that would be good. There is a reference implementation here: https://github.com/devinivy/fishbowl/blob/d0a535db41db15f39fffffd43ef8c02a9b8d51bf/packages/frontend/src/middle-end/helpers.js#L1-L17

• How do we feel about immediately firing onChange?
• How do we want to receive current and previous values, particularly for the initial call if onChange is fired immediately.
• Should we offer an alterate equality comparison?
• If so should the API work more like hook dependencies (compute a hash for direct comparison) or more like memoize-one's equality comparator (implement a function that receives two arguments and tells you if they're the same)?
• Should there be an additional interface to this utility baked into the middle-end's startup, or will these always be setup by hand in the initializer?