firebase - 在 Firebase 云函数中获取空值 onDelete()

Question

我在 onDelete() firebase 云函数中得到空值。下面是我的代码

 exports.jobSeekerToES=functions.database.ref('/Users/{userId}/userFileDetails/files/{fileKey}').onDelete(event=>
{

var file=event.data.val();
console.log("deleted file key"+event.params.fileKey);
console.log("deleted file "+file);  // file is null

});

它在日志上打印 fileKey。但文件为空请帮助我哪里错了

Answer 1

event.data.val() 返回删除后位置的值。对于 onDelete() 触发器，它将始终为 null。要获取删除之前的值，请使用 previous事件快照的属性:

exports.jobSeekerToES=functions.database.ref(
    '/Users/{userId}/userFileDetails/files/{fileKey}').onDelete(event=>
{

  var file=event.data.previous.val();  // <= CHANGED
  console.log("deleted file key"+event.params.fileKey);
  console.log("deleted file "+file);

});