如何将多个驱动程序与RxSwift正确组合？

Question

我正在将一个viewDidAppear和filter驱动程序与RxSwift 结合起来.他们工作得很好.但是当我引入第三个驱动程序时,它会停止调用flatMapLatest最新的组合.

在我的View Controller中,我有以下驱动程序:

let filter: Driver<String>
let viewDidAppear: Driver<Void>
let refresh: Driver<Void>

在我的视图模型中:

// On viewDidAppear, I download a list of portfolios

let viewDidAppearPortfolios = viewDidAppear
    .flatMapLatest({ (_) -> Driver<Result<[PortfolioModel]>> in        
        return networkService.request(Router.portfolios)!
            .responseCollections()
            .trackActivity(fetching)
            .asDriver(onErrorJustReturn: .failure(NSError()))

    })
    .flatMapLatest({ (result: Result<[PortfolioModel]>) -> Driver<[PortfolioModel]> in

        switch result {
        case .success(let value): return Driver.just(value)
        case .failure(_): return Driver.just([])
        }

    })

// Then I combine with a filter from my search bar.

self.portfolios = Driver.combineLatest(viewDidAppearPortfolios, filter)
    .flatMapLatest { (portfolios: [PortfolioModel], filter: String) -> Driver<[PortfolioModel]> in

        if filter.isEmpty {
            return Driver.just(portfolios)
        }

        return Driver.just(portfolios.filter({ (portfolio) -> Bool in
            portfolio.portfolio.localizedCaseInsensitiveContains(filter)
        }))

    }

以上作品!

网络请求一个投资组合列表,我能够在我输入客户端时过滤这些结果.

但是,我希望用户拉动刷新,并再次触发网络请求!所以,我结合我的刷新驱动程序.

还有这个:

Driver.combineLatest(viewDidAppearPortfolios, filter)

变成这样:

Driver.combineLatest(viewDidAppearPortfolios, filter, refresh)

问题!

相结合后,refresh将flatMapLatest是不再叫上viewDidAppear!只有我手动pullToRefresh.

Driver.combineLatest(viewDidAppearPortfolios, filter, refresh).flatMapLatest { _,_,_ in 
    // No longer get's called on viewDidAppear after combining with refresh
}

1. 将viewDidAppearPortfolios仍然执行,因此网络要求越来越叫!
2. 只有当我手动拉动刷新时才能获得我之前要求的投资组合列表...

知道为什么吗？

谢谢!

Answer 1

看起来你还refresh没有发出单个事件,所以combineLatest不计算.我试过这段代码来测试:

let one = Driver.just(1)
let two = Driver.just(2)
let three: Driver<Int> = .just(3)

let result = Driver.combineLatest(one, two, three)
    .flatMapLatest {
        return Driver.just($0 + $1 + $2)
    }

result.drive(onNext: {
    print($0)
})

这打印6但如果你使用let three: Driver<Int> = .empty()这不打印任何东西.所以我想你需要一种方法来设置refresh流的初始值.