Question

我使用Firebase如下：

Post--

    -Kwc6asRRI1SUqrigYeD                 <- First input
                       -> Date: 1:00pm
                       -> ID: 1
                       -> Content: Hello!
    -Kwc6fXQsN2xIQtHOofZ  
                       -> Date: 2:00pm
                       -> ID: 2
                       -> Content: How are you?
    -Kwc6fXQsN2xRO39LDPD                  <-Most recent one
                       -> Date: 3:00pm
                       -> ID: 3
                       -> Content: I am good.

这些是“推送”的，因此会生成一个唯一的密钥，可用于根据"most recent to old"（或ID:3到ID:1）显示它们。

现在，当我需要更新数据时，请说ID:1帖子的内容从"Hello"发送到"My name is Steve"，然后它仍然保持唯一键虽然这是最近的一次。

Post--

    -Kwc6asRRI1SUqrigYeD                 <-Most recent one
                       -> Date: 4:00pm
                       -> ID: 1
                       -> Content: My name is Steve
    -Kwc6fXQsN2xIQtHOofZ  
                       -> Date: 2:00pm
                       -> ID: 2
                       -> Content: How are you?
    -Kwc6fXQsN2xRO39LDPD                  
                       -> Date: 3:00pm
                       -> ID: 3
                       -> Content: I am good.

我想我可以删除帖子并设置一个新帖子，但这似乎效率低下，特别是如果我有更多关于每个孩子的数据。

有没有办法重新设置密钥以反映时间变化（如下所示）？

Post--

    -Kwc6fXQsN2xIQtHOofZ  
                       -> Date: 2:00pm
                       -> ID: 2
                       -> Content: How are you?
    -Kwc6fXQsN2xRO39LDPD                  
                       -> Date: 3:00pm
                       -> ID: 3
                       -> Content: I am good.

    -Kwc6asRRI1KDodkeixk                <-Most recent one
                       -> Date: 4:00pm
                       -> ID: 1
                       -> Content: My name is Steve

Answer 1

无法更新现有节点的密钥（请参阅1，2，3）。如果需要新密钥，则必须生成具有相同内容的新节点。

但在这种情况下，您似乎更希望保持数据结构不变，而是为每个帖子添加lastUpdated时间戳：

Post--
    -Kwc6asRRI1SUqrigYeD
                   -> Date: 1:00pm
                   -> lastUpdated: 1508215054096
                   -> ID: 1
                   -> Content: Hello!
    -Kwc6fXQsN2xIQtHOofZ  
                   -> Date: 2:00pm
                   -> lastUpdated: 1507610306270
                   -> ID: 2
                   -> Content: How are you?
    -Kwc6fXQsN2xRO39LDPD
                   -> Date: 3:00pm
                   -> lastUpdated: 1508128668412
                   -> ID: 3
                   -> Content: I am good.

使用此结构，您可以使用Firebase查询以您想要的顺序获取结果。在JavaScript中，这看起来像：

var ref = firebase.database().reference("Post");
ref.orderByChild("lastUpdated")
   .once("value")
   .then(function(snapshot) {
     snapshot.forEach(function(post) {
       console.log(snapshot.key+": "+snapshot.val().Content);
     });
   });

Firebase重置密钥

1 个答案: