已采納回答 / 慕數據021159
先上代碼：var name = Optional.some("daniel")??? ? name? = Optional.none首先：對題主提問中對表表述做一點點更正。也許更正了這個也就同時解決了題主對提問“就是說這個值是屬于Optional里面的‘.none類型 ’而他不是屬于Optional里面的‘.some類型 ’？”其中.‘.none類型 ’不應該稱之為一種“類型”，‘.some類型 ’也不應該稱之為一種“類型”。它們兩個都是“Optional類型”這種類型的一個枚舉值。順便說一下，至于“Op...
2019-01-13
swift 4.2.1
guard let preIndex = str.range(of: ",")?.lowerBound else {return nil} guard let sufIndex = str.range(of: ",")?.upperBound else{return nil}
guard let first = Double(str.prefix(upTo: preIndex)) else{return nil}
guard let second = Double(str.suffix(from: sufIndex)) else{return nil}
guard let preIndex = str.range(of: ",")?.lowerBound else {return nil} guard let sufIndex = str.range(of: ",")?.upperBound else{return nil}
guard let first = Double(str.prefix(upTo: preIndex)) else{return nil}
guard let second = Double(str.suffix(from: sufIndex)) else{return nil}
2018-11-17
let preIndex = str.range(of: ",")!.lowerBound
let sufIndex = str.range(of: ",")!.upperBound
let first = str.prefix(upTo: preIndex)
let second = str.suffix(from: sufIndex)
latitude = Double(first) ?? 0
longitude = Double(second) ?? 0
let sufIndex = str.range(of: ",")!.upperBound
let first = str.prefix(upTo: preIndex)
let second = str.suffix(from: sufIndex)
latitude = Double(first) ?? 0
longitude = Double(second) ?? 0
2018-11-17
