将 ReSwift 与子状态一起使用时，如何避免在更新另一个子状态时收到不需要的子状态更新？

Question

当使用ReSwift与子状态，如何避免接收到不想要子状态更新（SubstateA），更新另一个子状态（SubstateB）时

我虽然这是重点避风港子状态...

状态.swift

struct MainState: StateType {
    var subStateA: SubstateA?
    var subStateB: SubstateB?
}

struct SubstateA: StateType {
    let value: String
}

struct SubstateB: StateType {
    let value: String
}

商店.swift

let mainStore = ReSwift.Store<MainState>(reducer: { action, state -> MainState in

    var newState = state ?? MainState()

    switch action {

    case let anAction as UpdateSubstateA:
        newState.subStateA = newState.subStateA ?? SubstateA(value: anAction.value)

    case let anAction as UpdateSubstateB:
        newState.subStateB = newState.subStateB ?? SubstateB(value: anAction.value)

    default:
        break
    }
    return newState
}, state: nil)

Actions.swift

struct UpdateSubstateA: Action {
    let value:String
}

struct UpdateSubstateB: Action {
    let value:String
}

视图控制器.swift

class ViewController: UIViewController {

    override func viewWillAppear(_ animated: Bool) {

        mainStore.subscribe(self)  { $0.select { state in (state.subStateB ) } }

        mainStore.dispatch(UpdateSubstateA(value: "a"))
        mainStore.dispatch(UpdateSubstateB(value: "b"))
    }
}

extension ViewController: StoreSubscriber {

    func newState(state: SubstateB?) {
        print("SubstateB updated")
    }

    typealias StoreSubscriberStateType = SubstateB?
}

虽然我为 SubstateB 调度了一个更新操作，但当 SubstateA 更新时，我也会收到 newState 事件

安慰

SubstateB updated
SubstateB updated
SubstateB updated

Answer 1

问题很老，但也许答案对某人有用。

订阅可以是：

mainStore.subscribe(self)  { $0.select { $0.subStateB }.skipRepeats(==) }

SubstateB 应该符合 Equatable 协议：

extension SubstateB: Equatable {
    static func == (lhs: Self, rhs: Self) -> Bool {
        return lhs.value == rhs.value
    }
}

安慰：

SubstateB updated - nil (initial value)
SubstateB updated - value: "b"