我想检查Firebase中是否已有用户选择了用户名,并且我已经创建了一个功能checkUsernameAlreadyTaken(username: String) -> Bool
来执行此操作。
这是函数的代码:
func checkUsernameAlreadyTaken(username: String) -> Bool {
databaseRef.child("usernames").child("\(username)").observe(.value, with: { (snapshot) in
print(username)
if snapshot.exists() {
print("Snapshot exist")
self.alreadyTaken = true
}
})
if alreadyTaken == true {
print("Username already taken")
return false
}
else {
return true
}
}
问题是方法observe(_ eventType: FIRDataEventType, with block: (FIRDataSnapshot) -> Void) -> Uint
是异步方法,因此我无法使用您在上面看到的策略。但我无法从Firebase方法中返回值,因为它是一种无效方法...
我该如何解决这个问题?
还有一件事。如果连接错误或与服务器没有连接,我怎么能返回false?
答案 0 :(得分:3)
您必须自己使用异步完成处理程序并验证是否存在Internet连接:
func checkUsernameAlreadyTaken(username: String, completionHandler: (Bool) -> ()) {
databaseRef.child("usernames").child("\(username)").observe(.value, with: { (snapshot) in
print(username)
if snapshot.exists() {
completionHandler(false)
} else {
let connectedRef = FIRDatabase.database().reference(withPath: ".info/connected")
connectedRef.observe(.value, with: { snapshot in
if let connected = snapshot.value as? Bool, connected {
completionHandler(true)
} else {
completionHandler(false)
// Show a popup with the description
let alert = UIAlertController(title: NSLocalizedString("No connection", comment: "Title Internet connection error"), message: NSLocalizedString("No internet connection, please go online", comment: "Internet connection error saving/retriving data in Firebase Database"), preferredStyle: .alert)
let defaultOkAction = UIAlertAction(title: NSLocalizedString("No internet connection, please go online", comment: "Internet connection error saving/retriving data in Firebase Database"), style: .default, handler: nil)
alert.addAction(defaultOkAction)
self.present(alert, animated: true, completion: nil)
}
})
}
})
}
然后用:
调用你的方法checkIfUserExists(username: text, completionHandler: { (value) in
// ...
})