Firebase child_ added 只添加孩子 [英] Firebase child_added only get child added

问题描述

来自 Firebase API:

From the Firebase API:

Child 添加:此事件将为每个初始孩子触发一次在这个位置，每次有新的时候都会再次触发添加了孩子.

Child Added: This event will be triggered once for each initial child at this location, and it will be triggered again every time a new child is added.

一些代码:

listRef.on('child_added', function(childSnapshot, prevChildName) {
    // do something with the child
});

但是由于该函数为这个位置的每个孩子调用一次，有没有办法只获取实际添加的孩子?

But since the function is called once for each child at this location, is there any way to get only the child that was actually added?

推荐答案

要跟踪自某个检查点以来添加的内容而不获取以前的记录，您可以使用 endAt() 和 limit() 获取最后一条记录:

To track things added since some checkpoint without fetching previous records, you can use endAt() and limit() to grab the last record:

// retrieve the last record from `ref`
ref.endAt().limitToLast(1).on('child_added', function(snapshot) {

   // all records after the last continue to invoke this function
   console.log(snapshot.name(), snapshot.val());

});

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