Filter on updates not working about reswift

[DivineDominion]

@sarensw This is actually normal behavior (because even when you change a "leaf" in the state, the root value also changes). ReSwift offers to skip identical state updates when the states conform to Equatable. See: http://reswift.github.io/ReSwift/master/getting-started-guide.html#example-of-skipping-identical-state-updates

[sarensw]

@DivineDominion , thanks a lot for the quickly reply. Interesting. I tried with .skip(==) and it works. Coming from Typescript + Redux, this seems strange, though.

I took the following selector from some of my TypeScript code.

// only if the reference of .current changes, then update the component
const currentFile = useAppSelector(state => state.files.current)

// only if the length of the .files array changes, then update the component
const count = useAppSelector(state => state.files.files?.length)

So I can be very specific about the updates that I want to be notified about. And I don't have to skip same values (let alone make sure that Equatable is implemented.

No complains here. Just something that I have to learn.

One thing that I also noticed is that I can't just select any arbitrary property that I want. It feels like it has to be struct what I can filter on. But maybe I am also missing something here.

[DivineDominion]

@sarensw Swift is a bit stricter than vanilla JS when it comes to checking for value equality. It may be a good practice to slap "Equatable" onto all your subtypes just so you don't need to worry.

You can select arbitrary substates, but then you need to make them a Swift tuple. These suffer from not being equatable, so you get convenient substate selection but need to (!) add the .skip(==) manually. That's because for tuples between 2 and 6 elements, a == overload exists; but the tuple is not a type that ca conform to Equatable, so ReSwift can't skip it by default. See https://developer.apple.com/documentation/swift/equatable

Having said that:

We could copy the tuple == overload approach and offer substate selector overloads that do this by default, I believe. Requires tests, of course. If you'd be into that, let me know :)