Swift 4转换分段故障:11

Question

需要帮助将一些代码转换为Swift 4.开始获取错误并且不确定如何转换这段代码.我遇到的麻烦String和doubleValue.

let distanceInMeters: Double = userLocation.distance(from: businessLocation)
let distanceInMiles: Double = ((distanceInMeters.description as? String).doubleValue * 0.00062137)
let distanceLabelText = "\(distanceInMiles.string(2)) miles away"

Answer 1

你正在String不必要地来回转换.此外,您应该使用String格式化程序以给定的精度打印双精度数.

以下是更简洁的代码:

let distanceInMeters = userLocation.distance(from: businessLocation)
let distanceInMiles = distanceInMeters * 0.00062137
let distanceLabelText = String(format: "%.2f miles away", distanceInMiles)