使用Firebase控制台在Firebase中设置数组 [英] Setting arrays in Firebase using Firebase console

问题描述

我正在使用Firebase控制台为演示应用准备数据。其中一个数据项是与会者。参加者是一个阵列。我想在Firebase中添加一些与会者作为数组。我知道Firebase没有数组，但按键（按时间顺序）。我如何做准备样本数据？我目前的Firebase数据如下所示。

解决方案

Firebase数据库不存储数组。它存储字典/关联数组。所以最接近你可以得到：

pre $ 参加者：{
0：Bill Gates，
1：Larry Page，
2：James Tamplin
}


您可以在Firebase控制台中构建此结构。然后，当您使用其中一个Firebase SDK读取它时，它将被转换为数组。

  firebase.database（）一次（'价值'，功能（快照）{
 console.log（snapshot.val（））; 
 // [比尔盖茨，拉里页 ，James Tamplin] 
}）; 
  

所以这可能是你寻找的结果。但我建议阅读这篇博客文章，了解为什么如果不存储阵列，Firebase更喜欢它： https://firebase.googleblog.com/2014/04/best-practices-arrays-in-firebase.html 。

不要使用一个数组，当你真的需要一个集合

大多数开发人员实际上并没有试图存储一个数组，我想你的情况可能是其中之一。例如：Bill Gates可以两次参加吗？

 与会者：{
 0：Bill Gates，
 1：Larry Page，
 2：James Tamplin，
 3：Bill Gates
} 
  

$ b $如果不是的话，你必须在添加他之前检查他是否已经在数组中。

 如果（！attendees.contains（Bill Gates））{
 attendees.push（Bill Gates）; 
 
 
 
 $ b $ p 
 $ b 
这是一个明显的迹象，表明你的数据结构对于使用而言是次优的-案件。在添加新的孩子之前，必须检查所有现有的孩子将会限制可扩展性。在这种情况下，您真正​​需要的是一个集合：一个数据结构，其中每个孩子只能出现一次。在Firebase中，您的模型设置如下： 
 
 
 参加者：{
Bill Gates：true，
 Larry Page：true，
James Tamplin：true 
} 
  
现在，每当您尝试添加比尔盖茨第二次，这是一个无操作：
 
 
  attendees [比尔盖茨 ] = true; 
  
所以不必为唯一性需求编写代码，数据结构隐式地解决了这个问题。 > 
I am using Firebase console for preparing data for a demo app. One of the data item is attendees. Attendees is an array. I want to add a few attendees as an array in Firebase. I understand Firebase does not have arrays, but object with keys (in chronological order). How do I do that for preparing sample data? My current Firebase data looks like the below.
解决方案
The Firebase Database doesn't store arrays. It stores dictionaries/associate arrays. So the closest you can get is:
attendees: {
  0: "Bill Gates",
  1: "Larry Page",
  2: "James Tamplin"
}
You can build this structure in the Firebase Console. And then when you read it with one of the Firebase SDKs, it will be translated into an array.
firebase.database().ref('attendees').once('value', function(snapshot) {
  console.log(snapshot.val());
  // ["Bill Gates", "Larry Page", "James Tamplin"]
});
So this may be the result that you're look for. But I recommend reading this blog post on why Firebase prefers it if you don't store arrays: https://firebase.googleblog.com/2014/04/best-practices-arrays-in-firebase.html.


Don't use an array, when you actually need a set

Most developers are not actually trying to store an array and I think your case might be one of those. For example: can "Bill Gates" be an attendee twice? 
attendees: {
  0: "Bill Gates",
  1: "Larry Page",
  2: "James Tamplin",
  3: "Bill Gates"
}
If not, you're going to have to check whether he's already in the array before you add him.
if (!attendees.contains("Bill Gates")) {
  attendees.push("Bill Gates");
}
This is a clear sign that your data structure is sub-optimal for the use-case. Having to check all existing children before adding a new one is going to limit scalability.

In this case, what you really want is a set: a data structure where each child can be present only once. In Firebase you model sets like this:
attendees: {
  "Bill Gates": true,
  "Larry Page": true,
  "James Tamplin": true
}
And now whenever you try to add Bill Gates a second time, it's a no-op:
attendees["Bill Gates"] = true;
So instead of having to code for the uniqueness requirement, the data structure implicitly solves it.

                        
这篇关于使用Firebase控制台在Firebase中设置数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！