基本数据类型 转 字符串
let string = String(number);

let string = UIDevice.currentDevice().systemVersion;

_ = ( string as NSString ).doubleValue;

_ = ( string as NSString ).floatValue;

_ = ( string as NSString ).intValue;

_ = ( string as NSString ).integerValue;

_ = ( string as NSString ).boolValue;

//Int 64
_ = ( string as NSString ).longLongValue;