ios - 可选([值])!产生 nil (错误)，尽管它有一个值

Question

我有以下可选代码。

"\(postArray[indexPath.row].user.username)"

当我打印该值时，我得到类似以下内容的信息: 可选(“你好曼”)但是当我强制展开以摆脱Optional()时，应用程序崩溃了 零。为什么会发生这种情况？我该如何解决这个问题？

我打印:

    print(postArray[indexPath.row].user.username, " loop full\(indexPath.row)")
    print(postArray[indexPath.row].user.username!, " loop full\(indexPath.row)")

并得到如下结果

nil  loop full2

//这里崩溃

我将用户添加到每个帖子对象，如下所示:

    func retrieveUsersInfo(userObj: User) {

    let ref = Database.database().reference()

    if userObj.userID != nil {
        print("inside if of retrieveUsers")

        let UID = userObj.userID!
        print(UID, "<-- uid promg")
        let currentUID = "\(UID)"
        print(currentUID, "<<- current uid")
        print(lastUID, "<-- chhhc")

        if lastUID == nil {
            print("last uid 6was nil")
            ref.child("users2").child(UID).observe(.value, with: { (snapshot) in
                print(snapshot.childSnapshot(forPath: "username").value as! String, "0302310320101320312032101")

                print("here?")
                do {
                    self.addUserDataToObject(userObj: userObj, snapshot: snapshot)
                }

            })

        } else if currentUID == lastUID! {
            print("hello?")
            ref.child("users2").child(UID).observe(.value, with: { (snapshot) in
                print(snapshot.childSnapshot(forPath: "username").value as! String, "0302310320101320312032101")

                do {
                    self.addUserDataToObject(userObj: userObj, snapshot: snapshot)
                }

            })
        } else if currentUID != lastUID! {
            print("vai malandra") //the stuff below should be made into another function to reduce text; be more fficient
            ref.child("users2").child(UID).observe(.value, with: { (snapshot) in
                print(snapshot.childSnapshot(forPath: "username").value as! String, "0302310320101320312032101")

                do {
                    self.addUserDataToObject(userObj: userObj, snapshot: snapshot)
                }

            })

        } else {
            print("gggg")
        }
        lastUID = "\(UID)"
    }
}

波纹管使用的功能:

    func addUserDataToObject(userObj: User, snapshot: DataSnapshot) {
    if "\(snapshot.childSnapshot(forPath: "username").value as! String)" != nil {
        userObj.fullName = "\(snapshot.childSnapshot(forPath: "fullName").value as! String)"
        userObj.username = "\(snapshot.childSnapshot(forPath: "username").value as! String)"
        userObj.profileImageUrl = "\(snapshot.childSnapshot(forPath: "profileImage").value as! String)"
    } else {
        print("the username was nil!")
    }
}

对于我从 .childAdded 获得的每个用户(我从用户关注列表中获得)，我调用此方法

Answer 1

很可能在某些时候无法设置可选值。因此，您应该尝试使用 guard 或 if let 来确保您在设置值时获取该值，并避免在其为零时使应用程序崩溃。