如何在 Swift 中过滤 Firebase 数据? [英] How to filter Firebase data in Swift?

问题描述

基本上，我有一个称为主题的结构，其中包含 Title、Description 和 Published 标志(请参阅下面的屏幕截图以进行说明).

Basically, I have a structure called, topics which contains Title, Description and a Published flag (see screenshot below for clarification ).

在应用程序中，我想过滤数据，只显示具有published = true 的主题.

In the application, I want to filter the data and only show the topics that have published = true.

这就是我想要做的:

self.ref = FIRDatabase.database().referenceFromURL(FIREBASE_URL).child("topics")
        self.ref?.queryEqualToValue("published")
        self.ref?.observeEventType(.Value, withBlock: { (snapshot) in
            //...Handle Snapshot here
        })

但这行不通.我应该如何处理这个问题?预先感谢您的帮助.

But this is not working. How should I approach this? Thanks in advance for the help.

推荐答案

你有一些小错误.总体来说没什么太糟糕的，但结合起来他们永远不会工作:

You have a few small mistakes in there. Overall nothing too bad, but combined they'll never work:

1. 调用任何 query... 方法都会返回一个新对象
2. 你需要orderByChild()才能过滤它的值
3. 你需要遍历结果

1. calling any of the query... methods returns a new object
2. you need to orderByChild() before you can filter on its value
3. you need to loop over the results

结合这些:

let ref = FIRDatabase.database().referenceFromURL(FIREBASE_URL).child("topics")
let query = ref.queryOrderedByChild("published").queryEqualToValue(true)
query.observeEventType(.Value, withBlock: { (snapshot) in
    for childSnapshot in snapshot.children {
        print(childSnapshot)
    }
})

我们经常收到这个问题.例如，昨天的这看起来非常相似:Firebase 查询未正确执行.由于我的解释因每个答案而异，我建议浏览一下以阅读我的 相关答案 直到它点击.

We get this question regularly. For example, this from yesterday looks very similar: Firebase Query not Executing Properly. Since my explanation varies with every answer, I recommend browsing a bit to read my relevant answers until it clicks.

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