观察者未在快速的iOS Firebase实时数据库中调用 [英] Observer not calling in swift iOS firebase realtime database

问题描述

我正在构建一个使用Firebase实时数据库的应用程序.这是我的数据库内容.

I'm building an app which uses firebase realtime database. Here is my database content.

在这里，每当将一个新的子节点添加到请求"节点时，我都需要获取Phno和Message值并在控制台中将其打印出来.这是我的观察者代码

Here when ever a new child node is added to Request node I need to fetch the Phno and Message value and print it in the console. Here is my observer code

user.observe(.childAdded) { (DataSnapshot) in
       print("Inside")
       if let dict = DataSnapshot.value as? NSDictionary
       {
        for i in dict.allKeys
        {
            if let data = dict[i] as? NSDictionary
            {
                let message = data["Message"] as! String
                let phno = data["Phno"] as! String
                
                if(message != "" && phno != "")
                {
                    print(message)
                    print(phno)
                }
            
        }
       }
        
    }

我将上面的代码放在函数内，并在viewdidload()中首次调用它.之后，我尝试手动将子节点添加到请求节点，但观察者未触发.打印语句进行调试，我在日志输出中发现了一些奇怪的情况

I placed above code inside a function and called it in viewdidload() for first time. After which I tried manually adding child node to request node but the observer is not triggering.And I used that "inside" print statement for debugging and I found something strange in log output

您可以看到，在视图加载期间一次调用了Inside，但是再次调用了Inside，甚至没有对数据进行任何更改.如何解决此问题，以便在将新的子节点添加到请求节点时调用触发器

As you can see the Inside is called once during view did load but again it is called without even making any changes to the data. How can I solve this problem so that trigger get called when ever a new child node is added to request node

推荐答案

我认为问题在于，如何获取请求父节点中包含的子节点数据.如果是这样，请尝试以下操作:

I think the question is asking how to get to the child node data contained within the Request parent node. If so, try this:

首先，我们想在某个地方存储数据，所以我创建了一个类来保存每个请求，然后创建一个数组来保存所有请求

First, we want somewhere to store that data so I've created a class to hold each request and then an array to hold all of the requests

class RequestClass {
    var key = ""
    var msg = ""
    var phone = ""

    convenience init(withSnapshot: DataSnapshot) {
        self.init()
        self.key = withSnapshot.key
        self.msg = withSnapshot.childSnapshot(forPath: "Message").value as? String ?? "no msg"
        self.phone = withSnapshot.childSnapshot(forPath: "Phno").value as? String ?? "no phone"
    }
}

var requestArray = [RequestClass]()

然后，将观察者添加到请求"节点..childAdded观察者将首先迭代每个子项，然后呈现任何新添加的子项，此后又将其添加到数组中. self.ref 是一个指向我的Firebase根的类var.

Then we add an observer to the Request node. A .childAdded observer will initially iterate over each child and then present any newly added children thereafter which in turn will add it to the array. self.ref is a class var that points to my firebase root.

func readRequests() {
    let requestRef = self.ref.child("bill").child("Request")
    requestRef.observe(.childAdded, with: { snapshot in
        let request = RequestClass(withSnapshot: snapshot)
        self.requestArray.append(request)
    })
}

以上内容将读取问题中的节点并将每个请求存储在数组中.然后，要进行测试，我们可以将其打印出来

The above will read the node in the question and store each request in the array. Afterwards, to test, we can print those out

self.requestArray.forEach { print($0.key, $0.msg, $0.phone)}

输出为

EEC8A no message no phone
REQ2 Hello 2353476346346
REQ3 K 12312

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