用于 Bonjour Discovery 的 RxSwift 和嵌套订阅

Question

我对 Rx 非常陌生，并且一直在尝试制作一个解析服务的 Bonjour 发现客户端。这很简单，但我想尝试使用 RxSwift。

由于发现的 NSNetService 对象需要在解析之前被持久化，我不得不进行嵌套订阅调用，外部调用用于发现，内部调用用于解析......但有些事情告诉我这不是最好的方式。

import UIKit
import RxSwift

class BonjourClient: NSObject {

    let disposeBag = DisposeBag()
    var servicesArray = [NSNetService]()

    func startBrowsing() {
        let browser = NSNetServiceBrowser()
        browser.rx_netServiceBrowserDidFindServiceMoreComing
            .subscribeNext { (service: NSNetService) in
                        self.servicesArray.append(service)
                        self.servicesArray.last!.rx_netServiceDidResolveAddress
                            .subscribeNext { (sender: NSNetService) in
                                print("Resolved \(sender.name)")
                                let data = sender.TXTRecordData()
                                let dict: [String: NSData?] = NSNetService.dictionaryFromTXTRecordData(data!)
                                for (key, value) in dict {
                                    print("\(key) : \(String(data: value!, encoding: NSUTF8StringEncoding)!)")
                                }
                        }.addDisposableTo(self.disposeBag)
                        self.servicesArray.last!.resolveWithTimeout(5)
                }.addDisposableTo(disposeBag)
        browser.searchForServicesOfType("_amzn-wplay._tcp.", inDomain: "local.")
        NSRunLoop.currentRunLoop().run()
    }

}

我的代理类如下：

import UIKit
import RxSwift
import RxCocoa

class RxNSNetServiceBrowserDelegateProxy: DelegateProxy, NSNetServiceBrowserDelegate, DelegateProxyType {

    static func currentDelegateFor(object: AnyObject) -> AnyObject? {
        let browser: NSNetServiceBrowser = object as! NSNetServiceBrowser
        return browser.delegate
    }

    static func setCurrentDelegate(delegate: AnyObject?, toObject object: AnyObject) {
        let browser: NSNetServiceBrowser = object as! NSNetServiceBrowser
        browser.delegate = delegate as? NSNetServiceBrowserDelegate
    }

}

class RxNSNetServiceDelegateProxy: DelegateProxy, NSNetServiceDelegate, DelegateProxyType {

    static func currentDelegateFor(object: AnyObject) -> AnyObject? {
        let service: NSNetService = object as! NSNetService
        return service.delegate
    }

    static func setCurrentDelegate(delegate: AnyObject?, toObject object: AnyObject) {
        let service: NSNetService = object as! NSNetService
        service.delegate = delegate as? NSNetServiceDelegate
    }

}

extension NSNetServiceBrowser {

    public var rx_delegate: DelegateProxy {
        return proxyForObject(RxNSNetServiceBrowserDelegateProxy.self, self)
    }

    public var rx_netServiceBrowserDidFindServiceMoreComing: Observable<NSNetService> {
        return rx_delegate.observe("netServiceBrowser:didFindService:moreComing:")
            .map { params in
                let service = params[1] as! NSNetService
                return service
        }
    }

}

extension NSNetService {

    public var rx_delegate: DelegateProxy {
        return proxyForObject(RxNSNetServiceDelegateProxy.self, self)
    }

    public var rx_netServiceDidResolveAddress: Observable<NSNetService> {
        return rx_delegate.observe("netServiceDidResolveAddress:")
            .map { params in
                return params[0] as! NSNetService

        }
    }
}

如果我在browser.rx_netServiceBrowserDidFindServiceMoreComing 调用之后使用flatMap 而不是subscribeNext，则该服务将无法解析，因为我无法将它从flatMap 中持久化到一个数组中，原因我无法理解，主要来自从来没有碰过Rx。我必须使用嵌套调用吗？

我的问题的简短版本是上述作品，但对我来说似乎很复杂。任何想法将不胜感激。

Answer 1

您可以使用scan 来避免嵌套订阅。它会将rx_netServiceBrowserDidFindServiceMoreComing 中的每个NSNetService 添加到数组中。请注意，在这种情况下，您不必将 servicesArray 存储为成员变量，除非您出于其他原因需要它。

那么你可以使用flatMap如下：

browser.rx_netServiceBrowserDidFindServiceMoreComing
    .scan([NSNetService]()) { (services: [NSNetService], service: NSNetService)  in
        return services + [service]
    }.flatMap { (services: [NSNetService]) in
        return services.last!.rx_resolveWithTimeout(5)
    }.subscribeNext { (sender: NSNetService) in
        print("Resolved \(sender.name)")
        let data = sender.TXTRecordData()
        let dict: [String: NSData?] = NSNetService.dictionaryFromTXTRecordData(data!)
        for (key, value) in dict {
            print("\(key) : \(String(data: value!, encoding: NSUTF8StringEncoding)!)")
        }
}.addDisposableTo(disposeBag)

这需要在NSNetService 扩展中添加一个方法，因为您必须从flatMap 返回一个Observable：

extension NSNetService {
//existing methods omitted
 public func rx_resolveWithTimeout(timeout: NSTimeInterval) -> Observable<NSNetService> {
        self.resolveWithTimeout(timeout)
        return rx_netServiceDidResolveAddress.filter {
            $0 == self
        }
    }
}