Swift 2到3迁移String.fromCString

Question

我正在尝试将以下代码从此库(https://github.com/dankogai/swift-json)转换为Swift 3兼容代码.

关于fromCString以前在Swift 2中的String上可用的函数存在大量错误

到处都是错误大致相同:

'fromCString'不可用:请改用String.init？(validatingUTF8 :).请注意,它不再接受NULL作为有效输入.还要考虑使用String(cString :),它将尝试修复格式错误的代码单元.

因为我有两个选择可供选择我不确定给出原作者意图的正确选择.

例如,这是一个带错误的片段.

extension JSON : CustomStringConvertible {
    /// stringifies self.
    /// if pretty:true it pretty prints
    public func toString(pretty:Bool=false)->String {
        switch _value {
        case is NSError: return "\(_value)"
        case is NSNull: return "null"
        case let o as NSNumber:
            switch String.fromCString(o.objCType)! {
            case "c", "C":
                return o.boolValue.description
            case "q", "l", "i", "s":
                return o.int64Value.description
            case "Q", "L", "I", "S":
                return o.uint64Value.description
            default:
                switch o.doubleValue {
                case 0.0/0.0:   return "0.0/0.0"    // NaN
                case -1.0/0.0:  return "-1.0/0.0"   // -infinity
                case +1.0/0.0:  return "+1.0/0.0"   //  infinity
                default:
                    return o.doubleValue.description
                }
            }
        case let o as NSString:
            return o.debugDescription
        default:
            let opts = pretty ? JSONSerialization.WritingOptions.prettyPrinted : JSONSerialization.WritingOptions()
            if let data = (try? JSONSerialization.data(
                withJSONObject: _value, options:opts)) as NSData? {
                    if let result = NSString(
                        data:data as Data, encoding:String.Encoding.utf8.rawValue
                        ) as? String {
                            return result
                    }
            }
            return "YOU ARE NOT SUPPOSED TO SEE THIS!"
        }
    }
    public var description:String { return toString() }
}

请注意上面代码中的fromCString.正确模拟Swift 2行为的正确方法是什么？

Answer 1

因为错误建议使用init(cString:)这种方式.

String(cString:o.objCType)

有关详细信息,请查看Apple文档.