委托（delegate） iOS 开发中十分常见。不管是使用系统自带的库，还是一些第三方组件时，我们总能看到 delegate 的身影。使用 delegate 可以实现代码的松耦合，减少代码复杂度。但如果我们项目中使用 RxSwift，那么原先的 delegate 方式与我们链式编程方式就不相称了。
解决办法就是将代理方法进行一层 Rx 封装，这样做不仅会减少许多不必要的工作（比如原先需要遵守不同的代理，并且要实现相应的代理方法），还会使得代码的聚合度更高，更加符合响应式编程的规范。
其实在 RxCocoa 源码中我们也可以发现，它已经对标准的 Cocoa 做了大量的封装（比如 tableView 的 itemSelected）。下面我将通过样例演示如何将代理方法进行 Rx 化。
一、对 Delegate进行Rx封装原理
1，DelegateProxy
（1）DelegateProxy 是代理委托，我们可以将它看作是代理的代理。
（2）DelegateProxy 的作用是做为一个中间代理，他会先把系统的 delegate 对象保存一份，然后拦截 delegate 的方法。也就是说在每次触发 delegate 方法之前，会先调用 DelegateProxy 这边对应的方法，我们可以在这里发射序列给多个订阅者。
2，流程图
这里以 UIScrollView 为例，Delegate proxy 便是其代理委托，它遵守 DelegateProxyType 与 UIScrollViewDelegate，并能响应 UIScrollViewDelegate 的代理方法，这里我们可以为代理委托设计它所要响应的方法（即为订阅者发送观察序列）。
/***
+-------------------------------------------+
| |
| UIView subclass (UIScrollView) |
| |
+-----------+-------------------------------+
|
| Delegate
|
|
+-----------v-------------------------------+
| |
| Delegate proxy : DelegateProxyType +-----+----> Observable<T1>
| , UIScrollViewDelegate | |
+-----------+-------------------------------+ +----> Observable<T2>
| |
| +----> Observable<T3>
| |
| forwards events |
| to custom delegate |
| v
+-----------v-------------------------------+
| |
| Custom delegate (UIScrollViewDelegate) |
| |
+-------------------------------------------+
**/
二、获取地理定位信息样例
这个是 RxSwift 的一个官方样例，演示的是如何对 CLLocationManagerDelegate 进行 Rx 封装。
1，效果图
（1）第一次运行时会申请定位权限，如果当前App可以使用定位信息时，界面上会实时更新显示当前的经纬度。
（2）如果当前 App 被禁止使用定位信息，界面上会出现一个提示按钮，点击后会自动跳转到系统权限设置页面。
2，准备工作
（1）RxCLLocationManagerDelegateProxy.swift
首先我们继承 DelegateProxy 创建一个关于定位服务的代理委托，同时它还要遵守 DelegateProxyType 和 CLLocationManagerDelegate 协议。
import CoreLocation
import RxSwift
import RxCocoa
extension CLLocationManager: HasDelegate {
public typealias Delegate = CLLocationManagerDelegate
}
public class RxCLLocationManagerDelegateProxy
: DelegateProxy<CLLocationManager, CLLocationManagerDelegate>
, DelegateProxyType , CLLocationManagerDelegate {
public init(locationManager: CLLocationManager) {
super.init(parentObject: locationManager,
delegateProxy: RxCLLocationManagerDelegateProxy.self)
}
public static func registerKnownImplementations() {
self.register { RxCLLocationManagerDelegateProxy(locationManager: $0) }
}
internal lazy var didUpdateLocationsSubject = PublishSubject<[CLLocation]>()
internal lazy var didFailWithErrorSubject = PublishSubject<Error>()
public func locationManager(_ manager: CLLocationManager,
didUpdateLocations locations: [CLLocation]) {
_forwardToDelegate?.locationManager?(manager, didUpdateLocations: locations)
didUpdateLocationsSubject.onNext(locations)
}
public func locationManager(_ manager: CLLocationManager,
didFailWithError error: Error) {
_forwardToDelegate?.locationManager?(manager, didFailWithError: error)
didFailWithErrorSubject.onNext(error)
}
deinit {
self.didUpdateLocationsSubject.on(.completed)
self.didFailWithErrorSubject.on(.completed)
}
}
（2）CLLocationManager+Rx.swift
接着我们对 CLLocationManager 进行Rx 扩展，作用是将CLLocationManager与前面创建的代理委托关联起来，将定位相关的 delegate 方法转为可观察序列。
注意：下面代码中将 methodInvoked方法替换成 sentMessage 其实也可以，它们的区别可以看另一篇文章：
import CoreLocation
import RxSwift
import RxCocoa
extension Reactive where Base: CLLocationManager {
/**
Reactive wrapper for `delegate`.
For more information take a look at `DelegateProxyType` protocol documentation.
*/
public var delegate: DelegateProxy<CLLocationManager, CLLocationManagerDelegate> {
return RxCLLocationManagerDelegateProxy.proxy(for: base)
}
// MARK: Responding to Location Events
/**
Reactive wrapper for `delegate` message.
*/
public var didUpdateLocations: Observable<[CLLocation]> {
return RxCLLocationManagerDelegateProxy.proxy(for: base)
.didUpdateLocationsSubject.asObservable()
}
/**
Reactive wrapper for `delegate` message.
*/
public var didFailWithError: Observable<Error> {
return RxCLLocationManagerDelegateProxy.proxy(for: base)
.didFailWithErrorSubject.asObservable()
}
#if os(iOS) || os(macOS)
/**
Reactive wrapper for `delegate` message.
*/
public var didFinishDeferredUpdatesWithError: Observable<Error?> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didFinishDeferredUpdatesWithError:)))
.map { a in
return try castOptionalOrThrow(Error.self, a[1])
}
}
#endif
#if os(iOS)
// MARK: Pausing Location Updates
/**
Reactive wrapper for `delegate` message.
*/
public var didPauseLocationUpdates: Observable<Void> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManagerDidPauseLocationUpdates(_:)))
.map { _ in
return ()
}
}
/**
Reactive wrapper for `delegate` message.
*/
public var didResumeLocationUpdates: Observable<Void> {
return delegate.methodInvoked( #selector(CLLocationManagerDelegate
.locationManagerDidResumeLocationUpdates(_:)))
.map { _ in
return ()
}
}
// MARK: Responding to Heading Events
/**
Reactive wrapper for `delegate` message.
*/
public var didUpdateHeading: Observable<CLHeading> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didUpdateHeading:)))
.map { a in
return try castOrThrow(CLHeading.self, a[1])
}
}
// MARK: Responding to Region Events
/**
Reactive wrapper for `delegate` message.
*/
public var didEnterRegion: Observable<CLRegion> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didEnterRegion:)))
.map { a in
return try castOrThrow(CLRegion.self, a[1])
}
}
/**
Reactive wrapper for `delegate` message.
*/
public var didExitRegion: Observable<CLRegion> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didExitRegion:)))
.map { a in
return try castOrThrow(CLRegion.self, a[1])
}
}
#endif
#if os(iOS) || os(macOS)
/**
Reactive wrapper for `delegate` message.
*/
@available(OSX 10.10, *)
public var didDetermineStateForRegion: Observable<(state: CLRegionState,
region: CLRegion)> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didDetermineState:for:)))
.map { a in
let stateNumber = try castOrThrow(NSNumber.self, a[1])
let state = CLRegionState(rawValue: stateNumber.intValue)
?? CLRegionState.unknown
let region = try castOrThrow(CLRegion.self, a[2])
return (state: state, region: region)
}
}
/**
Reactive wrapper for `delegate` message.
*/
public var monitoringDidFailForRegionWithError:
Observable<(region: CLRegion?, error: Error)> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:monitoringDidFailFor:withError:)))
.map { a in
let region = try castOptionalOrThrow(CLRegion.self, a[1])
let error = try castOrThrow(Error.self, a[2])
return (region: region, error: error)
}
}
/**
Reactive wrapper for `delegate` message.
*/
public var didStartMonitoringForRegion: Observable<CLRegion> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didStartMonitoringFor:)))
.map { a in
return try castOrThrow(CLRegion.self, a[1])
}
}
#endif
#if os(iOS)
// MARK: Responding to Ranging Events
/**
Reactive wrapper for `delegate` message.
*/
public var didRangeBeaconsInRegion: Observable<(beacons: [CLBeacon],
region: CLBeaconRegion)> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didRangeBeacons:in:)))
.map { a in
let beacons = try castOrThrow([CLBeacon].self, a[1])
let region = try castOrThrow(CLBeaconRegion.self, a[2])
return (beacons: beacons, region: region)
}
}
/**
Reactive wrapper for `delegate` message.
*/
public var rangingBeaconsDidFailForRegionWithError:
Observable<(region: CLBeaconRegion, error: Error)> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:rangingBeaconsDidFailFor:withError:)))
.map { a in
let region = try castOrThrow(CLBeaconRegion.self, a[1])
let error = try castOrThrow(Error.self, a[2])
return (region: region, error: error)
}
}
// MARK: Responding to Visit Events
/**
Reactive wrapper for `delegate` message.
*/
@available(iOS 8.0, *)
public var didVisit: Observable<CLVisit> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didVisit:)))
.map { a in
return try castOrThrow(CLVisit.self, a[1])
}
}
#endif
// MARK: Responding to Authorization Changes
/**
Reactive wrapper for `delegate` message.
*/
public var didChangeAuthorizationStatus: Observable<CLAuthorizationStatus> {
return delegate.methodInvoked(#selector(CLLocationManagerDelegate
.locationManager(_:didChangeAuthorization:)))
.map { a in
let number = try castOrThrow(NSNumber.self, a[1])
return CLAuthorizationStatus(rawValue: Int32(number.intValue))
?? .notDetermined
}
}
}
fileprivate 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
}
fileprivate func castOptionalOrThrow<T>(_ resultType: T.Type,
_ object: Any) throws -> T? {
if NSNull().isEqual(object) {
return nil
}
guard let returnValue = object as? T else {
throw RxCocoaError.castingError(object: object, targetType: resultType)
}
return returnValue
}
（3）GeolocationService.swift
虽然现在我们已经可以直接 CLLocationManager 的 rx 扩展方法获取位置信息了。但为了更加方便使用，我们这里对 CLLocationManager 再次进行封装，定义一个地理定位的 service 层，作用如下：
- 自动申请定位权限，以及授权判断。
- 自动开启定位服务更新。
- 自动实现经纬度数据的转换。
import CoreLocation
import RxSwift
import RxCocoa
//地理定位服务层
class GeolocationService {
//单例模式
static let instance = GeolocationService()
//定位权限序列
private (set) var authorized: Driver<Bool>
//经纬度信息序列
private (set) var location: Driver<CLLocationCoordinate2D>
//定位管理器
private let locationManager = CLLocationManager()
private init() {
//更新距离
locationManager.distanceFilter = kCLDistanceFilterNone
//设置定位精度
locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
//获取定位权限序列
authorized = Observable.deferred { [weak locationManager] in
let status = CLLocationManager.authorizationStatus()
guard let locationManager = locationManager else {
return Observable.just(status)
}
return locationManager
.rx.didChangeAuthorizationStatus
.startWith(status)
}
.asDriver(onErrorJustReturn: CLAuthorizationStatus.notDetermined)
.map {
switch $0 {
case .authorizedAlways:
return true
default:
return false
}
}
//获取经纬度信息序列
location = locationManager.rx.didUpdateLocations
.asDriver(onErrorJustReturn: [])
.flatMap {
return $0.last.map(Driver.just) ?? Driver.empty()
}
.map { $0.coordinate }
//发送授权申请
locationManager.requestAlwaysAuthorization()
//允许使用定位服务的话，开启定位服务更新
locationManager.startUpdatingLocation()
}
}
3，使用样例
（1）要获取定位信息，首先我们需要在 info.plist 里加入相关的定位描述：
-
Privacy - Location Always and When In Use Usage Description：我们需要通过您的地理位置信息获取您周边的相关数据 -
Privacy - Location When In Use Usage Description：我们需要通过您的地理位置信息获取您周边的相关数据
（2）Main.storyboard
在 StoryBoard 中添加一个Label 和 Button，分别用来显示经纬度信息，以及没有权限时的提示。并将它们与代码做 @IBOutlet 绑定。
（3）UILabel+Rx.swift
为了能让 Label 直接绑定显示经纬度信息，这里对其做个扩展。
import RxSwift
import RxCocoa
import CoreLocation
//UILabel的Rx扩展
extension Reactive where Base: UILabel {
//实现CLLocationCoordinate2D经纬度信息的绑定显示
var coordinates: Binder<CLLocationCoordinate2D> {
return Binder(base) { label, location in
label.text = "经度: \(location.longitude)\n纬度: \(location.latitude)"
}
}
}
（4）ViewController.swift
主视图控制器代码如下，可以看到我们获取定位信息变得十分简单。
import UIKit
import RxSwift
import RxCocoa
class ViewController: UIViewController {
@IBOutlet weak private var button: UIButton!
@IBOutlet weak var label: UILabel!
let disposeBag = DisposeBag()
override func viewDidLoad() {
super.viewDidLoad()
//获取地理定位服务
let geolocationService = GeolocationService.instance
//定位权限绑定到按钮上(是否可见)
geolocationService.authorized
.drive(button.rx.isHidden)
.disposed(by: disposeBag)
//经纬度信息绑定到label上显示
geolocationService.location
.drive(label.rx.coordinates)
.disposed(by: disposeBag)
//按钮点击
button.rx.tap
.bind { [weak self] _ -> Void in
self?.openAppPreferences()
}
.disposed(by: disposeBag)
}
//跳转到应有偏好的设置页面
private func openAppPreferences() {
UIApplication.shared.open(URL(string: UIApplicationOpenSettingsURLString)!)
}
}
