Swift 3.0:无法推断当前上下文中的闭包类型PromiseKit

Question

我在swift 3.0中有以下代码,我在哪里使用PromiseKit.

func calculateTravelTime(from: CLLocation, to: CLLocation) -> Promise<Double> {
     Promise<Double> { completion, reject -> Void in
        let request = MKDirections.Request()
        request.transportType = .walking

        let fromPlacemark = MKPlacemark(coordinate: from.coordinate)
        let toPlacemark = MKPlacemark(coordinate: to.coordinate)

        let fromMapPoint = MKMapItem(placemark: fromPlacemark)
        let toMapPoint = MKMapItem(placemark: toPlacemark)

        request.source = fromMapPoint
        request.destination = toMapPoint
        request.requestsAlternateRoutes = false

        let directions = MKDirections(request: request)
        directions.calculate { response, error in
            if error != nil {
                reject(error!)
            } else {
                let time = (response?.routes.first?.expectedTravelTime ?? 0) / 60.0
               completion(time)
            }
        }

    }
} 

它在第二行给出以下错误:"无法在当前上下文中推断闭包类型"

错误代码行:

Promise<Double> { completion, reject -> Void in

我无法确定它为什么会出现此错误.有没有快速的专家可以帮助我.

谢谢!

Answer 1

在当前PromiseKit版本中

Promise<T> { fulfill, reject -> Void in }

改为

Promise<T> { seal -> Void in }

所以,你的新实现将改为这个,

func calculateTravelTime(from: CLLocation, to: CLLocation) -> Promise<Double> {
     Promise<Double> { seal -> Void in
        let request = MKDirections.Request()
        request.transportType = .walking

        let fromPlacemark = MKPlacemark(coordinate: from.coordinate)
        let toPlacemark = MKPlacemark(coordinate: to.coordinate)

        let fromMapPoint = MKMapItem(placemark: fromPlacemark)
        let toMapPoint = MKMapItem(placemark: toPlacemark)

        request.source = fromMapPoint
        request.destination = toMapPoint
        request.requestsAlternateRoutes = false

        let directions = MKDirections(request: request)
        directions.calculate { response, error in
            if error != nil {
                seal.reject(error!)
            } else {
                let time = (response?.routes.first?.expectedTravelTime ?? 0) / 60.0
               seal.fulfill(time)
            }
        }

    }
}