RxSwift 给代理添加Rx扩展

在RxCocoa里面封装了大量系统UI组件的扩展，我们可以仿照RxCocoa里面的封装方式，给自己的代理也添加Rx的扩展。

大概原理就是通过DelegateProxy把delegate的方法调用转换为一个observable sequence。

Av4gtx.png

这里我们用CLLocationManager代理的封装作为例子。

1.创建一个RXCLLocationManagerDelegateProxy类

open class RXCLLocationManagerDelegateProxy:
    DelegateProxy<CLLocationManager, CLLocationManagerDelegate>,
    DelegateProxyType,
    CLLocationManagerDelegate  {
    
    public weak private(set) var locationManager: CLLocationManager?
    
    public init(locationManager: ParentObject) {
        self.locationManager = locationManager
        super.init(parentObject: locationManager, delegateProxy: RXCLLocationManagerDelegateProxy.self)
    }
    
    public static func registerKnownImplementations() {
        self.register { RXCLLocationManagerDelegateProxy(locationManager: $0) }
    }
    
    public class func currentDelegate(for object: ParentObject) -> CLLocationManagerDelegate? {
        return object.delegate
    }
    
    public class func setCurrentDelegate(_ delegate: CLLocationManagerDelegate?, to object: ParentObject) {
        object.delegate = delegate
    }
}

2.让CLLocationManager遵循HasDelegate

extension CLLocationManager: HasDelegate {
    public typealias Delegate = CLLocationManagerDelegate
}

3.给CLLocationManager创建Reactive扩展

extension Reactive where Base: CLLocationManager {
    
    public var delegate: RXCLLocationManagerDelegateProxy {
        return RXCLLocationManagerDelegateProxy.proxy(for: base)
    }
    
    public var didUpdateLocations: ControlEvent<(manager: CLLocationManager, locations: [CLLocation])> {
        let sel = #selector(CLLocationManagerDelegate.locationManager(_:didUpdateLocations:))
    
        let source = delegate.methodInvoked(sel).map{ (args) -> (manager: CLLocationManager, locations: [CLLocation]) in
            let manager = try castOrThrow(CLLocationManager.self, args[0])
            let locations = try castOrThrow(Array<CLLocation>.self, args[1])
            return (manager, locations)
        }
        return ControlEvent(events: source)
    }
    
    public var didError: ControlEvent<(manager: CLLocationManager, error: Error)> {
        let didFailWithErrorSel = #selector(CLLocationManagerDelegate.locationManager(_:didFailWithError:))
        let didFinishDeferredUpdatesWithErrorSel = #selector(CLLocationManagerDelegate.locationManager(_:didFinishDeferredUpdatesWithError:))
        let generalError = delegate
            .methodInvoked(didFailWithErrorSel)
            .map(clErrorEvent)
        let updatesError = delegate
            .methodInvoked(didFinishDeferredUpdatesWithErrorSel)
            .map(clErrorEvent)
        let source = Observable.of(generalError, updatesError).merge()
        return ControlEvent(events: source)
    }
    
    private func clErrorEvent(_ args: [Any]) throws -> (manager: CLLocationManager, error: Error) {
        let manager = try castOrThrow(CLLocationManager.self, args[0])
        let error = try castOrThrow(Error.self, args[1])
        return (manager, error)
    }
    
    public var didErrorRangingBeacons: ControlEvent<(manager: CLLocationManager, region: CLBeaconRegion, error: Error)> {
        let rangingBeaconsDidFailForRegionSel = #selector(CLLocationManagerDelegate.locationManager(_:rangingBeaconsDidFailFor:withError:))
        let source = delegate
            .methodInvoked(rangingBeaconsDidFailForRegionSel)
            .map { (args) -> (manager: CLLocationManager, region: CLBeaconRegion, error: Error) in
                let manager = try castOrThrow(CLLocationManager.self, args[0])
                let beaconRegion = try castOrThrow(CLBeaconRegion.self, args[1])
                let error = try castOrThrow(Error.self, args[2])
                return (manager, beaconRegion, error)
            }
        return ControlEvent(events: source)
    }
    
}

注意

RxCocoa的 castOrThrow 这个方法没有加public修饰，所以我们是没法调用，我们需要Copy出来.

func castOrThrow<T>(_ resultType: T.Type, _ object: Any) throws -> T {
    guard let returnValue = object as? T else {
        throw RxCocoaError.castingError(object: object, targetType: resultType)
    }
    return returnValue
}

然后我们就可以使用了

llocationManager.rx
    .didUpdateLocations
    .subscribe(onNext: { (_, locations) in
        print(locations)
    })
    .disposed(by: disposeBag)

locationManager.rx
    .didError
    .subscribe(onNext: { (_, error) in
        print(error)
    })
    .disposed(by: disposeBag)

locationManager.rx
    .didErrorRangingBeacons
    .subscribe(onNext: { (_, beacons, _) in
        print(beacons)
    })
    .disposed(by: disposeBag)