我正在尝试通过协议(protocol)扩展实现 CLLocationManagerDelegate 协议(protocol)要求，但位置管理器在协议(protocol)扩展中看不到它并且失败了。但是，当移入该类时，它使用相同的代码。

这是我正在做的:

class ViewController: UIViewController, MyLocationProtocol {
    let locationManager = CLLocationManager()

    override func viewDidLoad() {
        super.viewDidLoad()

        locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers
        locationManager.distanceFilter = 1000.0
        locationManager.delegate = self

        // Below crashes when implementation in protocol extension
        locationManager.requestLocation()
    }

}

protocol MyLocationProtocol: CLLocationManagerDelegate {
    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
    func locationManager(manager: CLLocationManager, didFailWithError error: NSError)
}

extension MyLocationProtocol /*where Self: UIViewControll*/ { // Tried using where clause but still no go :(

    // Not being triggered by CLLocationManagerDelegate! :(
    // Move to ViewController class and error goes away
    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        print("MyLocationProtocol: locationManager: didUpdateLocations")
    }

    func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
        print("MyLocationProtocol: locationManager: didFailWithError")
    }

}

注意 extension MyLocationProtocol 我将 didUpdateLocations 和 didFailWithError 实现放在那里。他们从来没有得到触发，实际上崩溃说:'Delegate must respond to locationManager:didUpdateLocations:'。如果我将相同的 didUpdateLocations 和 didFailWithError 代码移动到 ViewController，一切都会按预期进行。

关于为什么这不能通过协议(protocol)扩展工作，我是否遗漏了什么？该类被认为符合 CLLocationManagerDelegate，否则它将在 locationManager.delegate = self 处失败。关于如何使这项工作有任何想法或某处是否存在错误？

最佳答案

协议(protocol)扩展是纯粹的 Swift 人员。协议(protocol)扩展的调度规则是:

如果变量的推断类型是协议(protocol)

• AND 方法在原始协议(protocol)中定义，然后调用运行时类型的实现，无论扩展中是否有默认实现。
• 并且该方法未在原始协议(protocol)中定义，然后调用默认实现。

如果变量的推断类型是类型 然后调用类型的实现。

考虑到所有这些......

import XCPlayground
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

import Foundation
import MapKit


class Lm: NSObject, CLLocationManagerDelegate {
    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [AnyObject]) {
        print("\(locations)")
    }
}


class C:Lm {
    let lm = CLLocationManager()
    override init() {
        super.init()
        lm.delegate = self
        lm.startUpdatingLocation()
    }

}
let c = C()
/*
2016-02-22 08:41:56.506 Untitled Page 10[32000:11547708] ### Failed to load Addressbook class CNContactNameFormatter
[<+48.71408491,+21.20868516> +/- 65.00m (speed -1.00 mps / course -1.00) @ 22/02/16 08 h 41 min 57 s Central European Standard Time]
[<+48.71408491,+21.20868516> +/- 65.00m (speed -1.00 mps / course -1.00) @ 22/02/16 08 h 41 min 57 s Central European Standard Time]
[<+48.71415732,+21.20859246> +/- 65.00m (speed -1.00 mps / course -1.00) @ 22/02/16 08 h 41 min 57 s Central European Standard Time]
....
*/

其他选择是做类似...

import XCPlayground
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

import Foundation
import MapKit

class MyLocationManager: CLLocationManager, CLLocationManagerDelegate {
    override init() {
        super.init()
        delegate = self
    }
}
extension MyLocationManager {
    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [AnyObject]) {
        print("\(locations)")
    }
}
class C {
    let lm = MyLocationManager()
    init() {
        lm.startUpdatingLocation()
    }
}

如果所有类型在编译时都是已知的并且协议(protocol)中没有“可选”方法，它会“按预期”工作

protocol P { func foo() }
extension P { func foo() { print("p") } }
protocol P1: P {}
extension P1 { func foo() { print("p1") } }
class C: P {}
class C1: P1 {}
let c = C()
let c1 = C1()
let p:P = C()
let p1:P = C1()

c.foo()  // p
c1.foo() // p1
p.foo()  // p
p1.foo() // p1

如需进一步阅读，请参阅 this和 this

关于ios - 协议(protocol)扩展不能满足 CLLocationManagerDelegate 一致性？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35525029/