(Swift) 如何正确解包可选值？身份验证后 Firebase uid 返回 nil

Question

我是 Swift 的新手，遇到 Firebase UID 方面的问题。

  usersReference.child("users").observeSingleEvent(of: FIRDataEventType.value, with: { (snapshot) in
            print(snapshot)
            if snapshot.hasChild((FIRAuth.auth()?.currentUser!.uid)!)
            {
                print("This user already exist")
            //code

                }

致命错误：在展开可选值时意外发现 nil

请指教，如何正确解包？还是别的？

Answer 1

您在展开两个可能为 nil 的值时没有首先检查它们是否为 nil

FIRAuth.auth()?.currentUser!

currentUser属性returns"The currently signed-in user (or null)."

(FIRAuth.auth()?.currentUser!.uid)!

要检查第一次或第二次解包是否导致了致命错误：解包可选值时意外发现 nil，重组您的if 语句如下：

if FIRAuth.auth()?.currentUser == nil {
    print("no user logged in")
} else if FIRAuth.auth()?.currentUser!.uid == null {
    print("no user id value")
} else if snapshot.hasChild((FIRAuth.auth()?.currentUser!.uid)!) {
    print("This user already exist")
} else {
    // code to handle new user
}

(Swift) 如何正确解包可选值？身份验证后 Firebase uid 返回 nil

(Swift) How unwrap the optional value properly? Firebase uid returning nil after authentication

uid

firebase

swift