如何基于选中的UIButton创建RxSwift序列及相关技术疑问

1. 基于UIControl的isSelected属性创建点击序列 #

通过监听按钮的rx.tap事件，每次点击切换isSelected状态，并将状态变化转化为可观察序列，同时用startWith初始化初始状态：

// 第一个按钮的选中状态序列
let firstButtonSelection = firstButton.rx.tap
    .map { [weak firstButton] in
        firstButton?.isSelected.toggle()
        return firstButton?.isSelected ?? false
    }
    .startWith(firstButton.isSelected)

// 第二个按钮的选中状态序列
let secondButtonSelection = secondButton.rx.tap
    .map { [weak secondButton] in
        secondButton?.isSelected.toggle()
        return secondButton?.isSelected ?? false
    }
    .startWith(secondButton.isSelected)

// 第三个按钮的选中状态序列
let thirdButtonSelection = thirdButton.rx.tap
    .map { [weak thirdButton] in
        thirdButton?.isSelected.toggle()
        return thirdButton?.isSelected ?? false
    }
    .startWith(thirdButton.isSelected)

2. 不可变Model的可观察模型更新方案 #

由于Model是不可变值类型，每次状态变化需要创建新实例。使用BehaviorRelay持有当前模型状态（替代原有的只读Observable<Model>），合并三个按钮的状态序列生成新模型并更新Relay：

步骤1：替换为BehaviorRelay存储模型 #

// 初始化初始模型（可结合本地存储读取，见问题3）
let initialModel = Model(isFirstButtonSelected: false, isSecondButtonSelected: false, isThirdButtonSelected: false)
let modelRelay = BehaviorRelay(value: initialModel)
let model: Observable<Model> = modelRelay.asObservable()

步骤2：合并状态序列更新模型 #

Observable.combineLatest(firstButtonSelection, secondButtonSelection, thirdButtonSelection)
    .subscribe(onNext: { firstSelected, secondSelected, thirdSelected in
        // 创建新的Model实例
        let newModel = Model(
            isFirstButtonSelected: firstSelected,
            isSecondButtonSelected: secondSelected,
            isThirdButtonSelected: thirdSelected
        )
        // 更新Relay，发送新模型
        modelRelay.accept(newModel)
    })
    .disposed(by: disposeBag)

步骤3：订阅模型变化更新UI #

model.subscribe(onNext: { [weak self] model in
    self?.configure(model)
})
.disposed(by: disposeBag)

3. 选中值的存储与恢复 #

以UserDefaults为例，让Model遵守Codable协议实现序列化存储：

步骤1：让Model遵守Codable #

struct Model: Codable {
    let isFirstButtonSelected: Bool
    let isSecondButtonSelected: Bool
    let isThirdButtonSelected: Bool
}

步骤2：模型变化时保存到UserDefaults #

modelRelay.subscribe(onNext: { model in
    do {
        let data = try JSONEncoder().encode(model)
        UserDefaults.standard.set(data, forKey: "SelectedButtonsModel")
    } catch {
        print("保存选中状态失败：\(error)")
    }
})
.disposed(by: disposeBag)

步骤3：初始化时读取保存的状态 #

var initialModel = Model(isFirstButtonSelected: false, isSecondButtonSelected: false, isThirdButtonSelected: false)
// 读取本地存储的状态
if let savedData = UserDefaults.standard.data(forKey: "SelectedButtonsModel") {
    do {
        initialModel = try JSONDecoder().decode(Model.self, from: savedData)
    } catch {
        print("读取选中状态失败：\(error)")
    }
}
let modelRelay = BehaviorRelay(value: initialModel)
let model: Observable<Model> = modelRelay.asObservable()

额外：Next按钮启用状态联动 #

合并三个选中序列，判断是否至少有一个按钮选中，绑定到Next按钮的isEnabled：

Observable.combineLatest(firstButtonSelection, secondButtonSelection, thirdButtonSelection)
    .map { $0 || $1 || $2 }
    .bind(to: nextButton.rx.isEnabled)
    .disposed(by: disposeBag)

内容的提问来源于stack exchange，提问作者nsus