在swift3中保存时，如何将JSON数据获取为nil？

代码：

var json: AnyObject?
do {
    json = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? [String:Any] as AnyObject?
    let UserID = json?["UserID"] as? [String:AnyObject]
    print(UserID) //printing nil

}
catch {
    print(error)
}

---

假设JSON的根对象是字典，

userID

的值可能是字符串

do {
    if let json = try JSONSerialization.jsonObject(with: data!, options: []) as? [String:Any] {
        if let userID = json["UserID"] as? String { // or as? Int if the user id is an integer
           print(userID)
        }
    }
}
catch {
    print(error)
}

如果根对象被假定为集合类型，则

.allowFragments

是无意义的