从异步完成处理程序返回的 RXSwift 平面图

Question

我正在尝试创建一个 searchBar，它通过带有请求的 MKLocalSearch 搜索地址并使用 RXSwift 并绑定到 RXCocoa

到目前为止，我已经完成了以下工作 1.过滤和去抖动以避免过多的请求：

let searchRes = searchBar.rx.text
    .orEmpty
    .filter { query in
        return query.characters.count > 4
    }
    .debounce(1, scheduler: MainScheduler.instance)

1. 生成的字符串查询被 map:ed 创建一个 MKLocationSearch，然后 flatMapp:ed 返回一个 MKMapItems 数组，以便能够将该数组绑定到 tableView 的项目：

   searchRes.map{query -> MKLocalSearch in
       let request = MKLocalSearchRequest()
       request.naturalLanguageQuery = query
       request.region = self.mapView.region
       return MKLocalSearch(request: request)
   }.flatMapLatest{search -> Observable<[MKMapItem]> in
       search.start(completionHandler:{(response, error) in
           let items: Variable<[MKMapItem]> = Variable([])
           if let resp = response {
               //need to return the result form this
               // i.e. items.value = response.mapItems
           }
           //can not return from here since the request is async
       }
   }.bindTo //continue to bind to tableview
   

如何使用 RXSwift 做到这一点，我找不到任何相关示例

Answer 1

您必须使用异步请求创建一个 Observable。您可以定义以下方法来做到这一点：

func mapItems(for searchRequest: MKLocalSearch) -> Observable<[MKMapItem]> {
    return Observable.create { observer in
        searchRequest.start(completionHandler: { (response, error) in
            if let error = error {
                observer.onError(error)
            } else {
                let items = response?.mapItems ?? []
                observer.onNext(items)
                observer.onCompleted()
            }
        })

        return Disposables.create {
            searchRequest.cancel()
        }
    }
}

那么你就可以用flatMapLatest这个方法了：

searchRes
    .map { query -> MKLocalSearch in
        let request = MKLocalSearchRequest()
        request.naturalLanguageQuery = query
        request.region = self.mapView.region
        return MKLocalSearch(request: request)
    }
    .flatMapLatest{ [unowned self] search -> Observable<[MKMapItem]> in
        self.mapItems(for: search)
    }
    .bindTo(....