我正在运行下面的代码以查看打开该应用程序的用户是否已登录,然后检查他们是否设置了配置文件。我无法检查来自档检查Firebase检查空值(Swift)
override func viewDidLoad() {
super.viewDidLoad()
//Check to see if user is already logged in
//by checking Firebase to see if authData is not nil
if ref.authData != nil {
//If user is already logged in, get their uid.
//Then check Firebase to see if the uid already has a profile set up
let uid = ref.authData.uid
ref.queryOrderedByChild("uid").queryEqualToValue(uid).observeSingleEventOfType(.Value, withBlock: { snapshot in
let profile = snapshot.value
print(profile)
})
返回在最后一行时,我打印(配置文件)的空值的值,我要么得到的资料信息,或
<null>
如何我检查这个值吗?
if profile == nil
不起作用
如果我做
let profile = snapshot.value as? String
第一,那么它总是返回零即使有一个snapshot.value
尝试,如果(snapshot.value!=无){}或者(snapshot.value作为!NSObject的!=无){} –
谢谢shrikant,但第一有同样的问题。第二个建议给我“值类型'NSObject永远不可为零”错误 – FortuneFaded
什么是快照的数据类型? –