Reswift: It is possible for ReSwift to have Selector?

[mortyccp]

In Redux, there is a “selector” library . It makes computing derived property from state more performance and thus encouraging minimal possible state. I think this fit very well into the current sub-state subscription.

I am not sure weather we can implement similar thing in Swift.But If its possible, I think its a good function to have in ReSwift.

[wpK]

@soapsign I agree.

If we want syntax like the following:

let shopItemsSelector: (AppState) -> [Item] = { state in return state.shop.items }
let taxPercentSelector: (AppState) -> Int = { state in return state.shop.taxPercent }

let subtotalSelector = createSelector(shopItemsSelector, { (items: [Item]) in
    return items.reduce(0, combine: {$0 + $1.value})
})

let taxSelector = createSelector(subtotalSelector, taxPercentSelector, { (subtotal, taxPercent) in
    return subtotal * (taxPercent / 100)
})

let totalSelector = createSelector(subtotalSelector, taxSelector, { (subtotal, tax) in
    return subtotal + tax
})

Then there would need to be a createSelector() function, with X parameters. Something like this (example without any kind of memoization):

func createSelector<State, S1, R>(p1: (State) -> S1, _ returnFunc: (S1) -> R) -> (State) -> R {
  return { (state) in
    return returnFunc(p1(state))
  }
}

func createSelector<State, S1, S2, R>(p1: (State) -> S1, _ p2: (State) -> S2, _ returnFunc: (S1, S2) -> R) -> (State) -> R {
  return { (state) in
    return returnFunc(p1(state), p2(state))
  }
}

func createSelector<State, S1, S2, S3, R>(p1: (State) -> S1, _ p2: (State) -> S2, p3: (State) -> S3, _ returnFunc: (S1, S2, S3) -> R) -> (State) -> R {
  return { (state) in
    return returnFunc(p1(state), p2(state), p3(state))
  }
}

Anyone else have a better way of doing this? I could throw up a simple project using something close to what you see above if you're interested in giving it a shot.

[wpK]

Created the project to get a better understanding of what kind of issues we might face. https://github.com/wpK/reswelect