RxSwift - 同时在两个 ViewControllers 接收相同的事件答案

【问题标题】：RxSwift - Receive the same event at two ViewControllers at the same timeRxSwift - 同时在两个 ViewControllers 接收相同的事件
【发布时间】：2022-09-29 01:08:48
【问题描述】：

嗨，我刚刚开始使用 RxSwift，并决定制作简单的货币兑换应用程序。我的应用程序有两个视图（allCurrenciesList 和 userFavouritesView）。基本上所有逻辑都有效，但前提是我每次都运行网络功能，其中一个是查看 didAppear/didLoad。我的观点是两次只取一次，并在必要时收到多次。应用程序获取货币字典并在 ViewModel 中将其传递给 BehaviorSubject，当视图加载/出现时，只需订阅它，并在 UITableView 中使用它。谢谢

class ListViewModel {
    
    let service: CurrencyService!
    var curriencies = BehaviorRelay<[Currency]>(value: [])
    var currienciesObservable: Observable<[Currency]> {
        return curriencies.asObservable().share()
    }
    let disposeBag = DisposeBag()
 
    init(service: CurrencyService) {
        self.service = service
    }
    
    func fetchAllCurrencies() {
      
            self.service.fetchAllSymbols { result in
                switch result{
                case .success(let currencies):
                    self.dictionaryIntoArray(currencies: currencies[\"symbols\"] as! [String : Any])
                case .failure:
                    print(\"error\")
                    
                }
            }
    }
    
    private func dictionaryIntoArray(currencies: [String: Any]) {
        var currencyArray = [Currency]()
        for (symbol, name) in currencies {
            currencyArray.append(Currency(symbol: symbol, fullName: name as! String))
        }
        let sortedArray = currencyArray.sorted { $0.fullName < $1.fullName }
        self.curriencies.accept(sortedArray)
    }

所有货币列表

override func viewDidLoad() {
        super.viewDidLoad()
        setupView()
        configureTableViewDataSource()
        tableView.delegate = self
        fetchData()
    }
    
    private func fetchData() {
        viewModel.fetchAllCurrencies() // this func is necceserry everysingle time 
        viewModel.currienciesObservable.subscribe(onNext: { curriencies in
            self.applySnapshot(curriencies: curriencies)
        }).disposed(by: disposeBag)
    }

用户收藏查看

 override func viewDidLoad() {
        super.viewDidLoad()
       
        viewModel.fetchAllCurrencies() // this func is necceserry everysingle time 
        viewModel.currienciesObservable.subscribe(onNext: { allCurencies in
            let selectedItems = UserDefaults.standard.array(forKey: \"SelectedCells\") as? [Int] ?? [Int]()
            var currenciesArray: [Currency] = []
            selectedItems.forEach { int in
                self.pickerValues.append(allCurencies[int])
                currenciesArray.append(allCurencies[int])
            }
            self.applySnapshot(curriencies: currenciesArray)
        }).disposed(by: disposeBag)
        
    }

标签： ios swift rx-swift

【解决方案1】：

这里的关键是不使用主题。不建议经常使用它们。只需直接定义currienciesObservable。

像这样的东西：

class ListViewModel {
    let currienciesObservable: Observable<[Currency]>

    init(service: CurrencyService) {
        self.currienciesObservable = service.rx_fetchAllSymbols()
            .map { currencies in
                currencies["symbols"]?.map { Currency(symbol: $0.key, fullName: $0.value as! String) }
                    .sorted(by: { $0.fullName < $1.fullName }) ?? []
            }
    }
}

extension CurrencyService {
    func rx_fetchAllSymbols() -> Observable<[String: [String: Any]]> {
        Observable.create { observer in
            self.fetchAllSymbols { result in
                switch result {
                case let .success(currencies):
                    observer.onNext(currencies)
                    observer.onCompleted()
                case let .failure(error):
                    observer.onError(error)
                }
            }
            return Disposables.create()
        }
    }
}

有了以上内容，每次订阅currenciesObservable 时，都会调用 fetch。

【讨论】：

【解决方案2】：

据我了解，这是因为您的 fetchAllSymbols 函数未存储在 DisposeBag 中。

func fetchAllCurrencies() {
    self.service.fetchAllSymbols { result in
         switch result{
            case .success(let currencies):
                self.dictionaryIntoArray(currencies: currencies["symbols"] as! [String : Any])
            case .failure:
                print("error")
                
         }
    }.dispose(by: disposeBag)
}

【讨论】：