如何在Swift中的多个节点中观察Firebase子值的变化? [英] How can I observe Firebase child value changes in multiple nodes in Swift?

问题描述

我的Firebase数据库中有一个用户"节点.其中的每个用户都有一个带有uid的根.每个用户的属性之一是坐标".我想为所有用户观察这些坐标中的任何变化.我几乎需要像这样的东西:

I have a "users" node in my Firebase database. Each user in it has a root with a uid for it. One of the properties of each user is "coordinates". I want to observe any change in any of those coordinates for all users. I almost need something like:

usersDatabaseReference.child("*").child("coordinates").observe(.value, with: { (snapshot) in 

我的结构如下:

• 用户

• users

• abcdefghijklmnop

• abcdefghijklmnop

• 坐标:"12.345,12.345"

• coordinates: "12.345,12.345"

其他道具

qrstuvwxyz

qrstuvwxyz

• 坐标:"34.567,34.567"

• coordinates: "34.567,34.567"

其他道具

因此，我正在寻找坐标值更改的所有用户的全局通知.

So I'm looking for a global notification for any user whose coordinates value changes.

我是否需要遍历userDatabaseReference中的所有子项，并为每个子项设置观察者?然后，无论何时添加或删除用户，都重新设置一次?

Do I need to loop through all children in my userDatabaseReference and set observers for each? And then any time a user is added or removed, set it all up again?

您可以看到为什么我要使用通配符.我应该如何处理?

You can see why I'd like to use a wildcard. How should I approach this?

推荐答案

您可以观察整个用户结构，然后使用快照确定坐标是否为已更改的元素

You could just observe the users structure as a whole, then use the snapshot to determine if the coordinate is the element that has changed

usersDatabaseReference.child("users").observe(.childChanged, with: { (snapshot) in
        //Determine if coordinate has changed
 })

您还可以做的是:

func observeChildAdded(){
    usersDatabaseReference.child("users").observe(.childAdded, with: { (snapshot) in
        //Get the id of the new user added
        let id = "123"
        self.usersDatabaseReference.child("users").child(id).observe(.childChanged, with: { (snapshot) in
            self.foundSnapshot(snapshot)
        })
    })
}

func foundSnapshot(_ snapshot: DataSnapshot){
    let idChanged = snapshot.key
    //Process new coordinates
}

因此，每当您添加一个新子项时，它都会自动为其设置观察者，但是它们都被推送到了同一个函数foundSnapshot

So that whenever you add a new child it automatically sets up an observer for it, but they all get pushed to the same function foundSnapshot

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