[英]Make AuthListener wait until for loop has finished
我在每次登录时都会读取用户的数据。 由于我在AppDelegate.swift中有一个Firebase AuthListener,因此一旦用户登录,视图就会发生变化。
问题是,在某些情况下,视图的变化速度比处理数据的速度快,导致没有所需数据的屏幕。
在过去,我通过向更改视图的代码添加: databaseRef.observeSingleEvent(of: .value, with: { snap in ... })
来绕过这个:
if user != nil && currentCar == "auto auswählen" {
databaseRef.observeSingleEvent(of: .value, with: { snap in
if user?.isAnonymous == false {
let controller = storyboard.instantiateViewController(withIdentifier: "RootPageViewController") as! RootPageViewController
let vc = storyboard.instantiateViewController(withIdentifier: "ProfileViewController") as! ProfileViewController
vc.readTimeline()
self.window?.rootViewController = controller
self.window?.makeKeyAndVisible()
} else if user?.isAnonymous == true {
let controller = storyboard.instantiateViewController(withIdentifier: "RootPageViewController") as! RootPageViewController
self.window?.rootViewController = controller
self.window?.makeKeyAndVisible()
}
})
这工作正常,但现在我在for循环的帮助下读取了我的数据,因为数据库请求早于for循环完成,所以不会:
databaseRef.child("users").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
for n in 1...snapshot.childrenCount {
databaseRef.child("users/\(uid)").child(String(n)).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
...
}) { (error) in
print(error.localizedDescription)
}
}
}) { (error) in
print(error.localizedDescription)
}
}
如何使AppDelegate.swift和AuthListener等到for循环结束?
您希望等到转到新视图,直到加载所有数据。 一种方法是计算已加载的子节点数,然后在加载所有子节点时继续。
在看起来像这样的代码中:
databaseRef.child("users").child(uid).observeSingleEvent(of: .value, with: { (snapshot) in
let value = snapshot.value as? NSDictionary
let loadedCount = 0
for n in 1...snapshot.childrenCount {
databaseRef.child("users/\(uid)").child(String(n)).observeSingleEvent(of: .value, with: { (snapshot) in
loadedCount = loadedCount + 1
let value = snapshot.value as? NSDictionary
...
if (loadedCount == snapshot.childrenCount) {
// TODO: all data is loaded, move to the next view
}
}) { (error) in
print(error.localizedDescription)
}
}
}) { (error) in
print(error.localizedDescription)
}
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