Swift 2 to 3 Migration String.fromCString

Question

I'm attempting to convert the following code from this library (https://github.com/dankogai/swift-json) into Swift 3 Compatible code.

There are a multitude of errors regarding the fromCString function that was previously available on the String in Swift 2

The error is roughly the same everywhere:

'fromCString' is unavailable: Please use String.init?(validatingUTF8:) instead. Note that it no longer accepts NULL as a valid input. Also consider using String(cString:), that will attempt to repair ill-formed code units.

Seeing as I have 2 choices to choose from I'm not sure the correct one given the original authors intentions.

For example here is a snippet with the error.

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() }
}

Notice fromCString in the above code. What is the correct way to simulate the Swift 2 behavior correctly?

Answer 1

As error suggest use init(cString:) like this way.

String(cString:o.objCType)

Check Apple Documentation for more detail.