试图从firebase获取变量的快照给我一个错误 [英] Trying to get a snapshot of a variable from firebase gives me an error

问题描述

在我使用本机和firebase做的社交媒体应用中，我试图获取评论数量post使用我保存在服务器上的变量的快照功能，然后当用户添加新注释时，我将向此变量添加一个。我这样做的代码就在这里：

In a social media app I am making with react native and firebase, I am trying to grab the number of comments a post has using the snapshot function of a variable I have saved on my servers, then I am going to add one to this variable when a user adds a new comment. My code to do so is right here:

firebase.database().ref('posts').child(this.state.passKey).update({
   comments: firebase.database().ref('posts/'+this.state.passKey).child('comments').snapshot.val() + 1 
})

当我实际运行此代码时，我收到错误消息：

When I actually run this code, I get an error saying:

Reference.child failed: First argument was an invalid path = "undefined".
Paths must be non-empty strings and can't contain ".","#","$","[", or "["

起初我认为这可能是this.state.passKey实际上没有传递密钥，而是放入我从服务器复制的密钥解决问题。

At first I thought this might be that the "this.state.passKey" wasn't actually passing the key, but putting in a key I copied from the server didn't fix the problem.

我的服务器
-

My Server -

推荐答案

要获得特定帖子的评论，你应该这样做

To get the comments of particular post you should do like this

let postId='someId'

postRef=`/posts/${postId}`
firebase.database().ref(postRef).once("value", dataSnapshot => {
comment=dataSnapshot.val().comments
  });

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