Firebase onWrite 不会触发

Nik 发表于 Dev

一世

我正在尝试使用onWritefordb_uppercaseLog但它不会触发。当我使用时onCreate，它确实会触发。

db_uppercaseLog侦听添加到的新日志/log/:pushId/original并创建日志的大写版本/log/:pushId/uppercase

onCreate((snapshot,context)=>{...} // works fine
onWrite((snapshot,context)=>{...} // did not work

我已经阅读了文档和参考资料。在stackoverflow上也读过类似的问题。但我无法与我的案子联系起来。这应该是教科书的例子吧？

我在这里做错了什么？


// Take the text parameter passed to this HTTP endpoint and insert it into the
// Realtime Database under the path /log/:pushId/original
// <host>/pushLog?text=
exports.pushLog=functions.https
.onRequest(async(req,res)=>{
  // Grab the text parameter.
  const original = req.query.text;
  // Push the new log into the Realtime Database using the Firebase Admin SDK.
  const snapshot = await admin.database().ref('/log').push({original: original});
  res.status(200).send(
    `<!doctype html><head><title>pushLog</title></head><body>
      <a href="${snapshot.ref.toString()}" target="_blank">${original} was saved</a>
    </body></html>`
  );
});

// Listens for new log added to /log/:pushId/original and creates an
// uppercase version of the log to /log/:pushId/uppercase
exports.db_uppercaseLog=functions.database
.ref('/log/{pushId}/original')
.onWrite((snapshot,context)=>{
  // Grab the current value of what was written to the Realtime Database.
  const original = snapshot.val();
  const uppercase = original.toUpperCase();
  // You must return a Promise when performing asynchronous tasks inside a Functions such as
  // writing to the Firebase Realtime Database.
  // Setting an "uppercase" sibling in the Realtime Database returns a Promise.
  return snapshot.ref.parent.child('uppercase').set(uppercase);
});

编码员

您的问题源于此onWrite，以onCreate 不同的方式处理数据，并且定义与您的问题不同。

onCreate((snapshot,context)=>{...})
onWrite((change,context)=>{...})

特别是，一个Change 对象是一个容器，它包含属性after和before，代表触发函数的状态变化。

与onWrite更改处理程序一样 - 如果不进行审核，它可以重新触发自身进入无限循环。在上面的代码中，这不是问题，但需要注意。但是当值被删除时你的代码会被触发，所以决定你希望如何处理它。

// Listens for changes at /log/:pushId/original and creates an
// uppercase version of the log at /log/:pushId/uppercase
exports.db_uppercaseLog=functions.database
.ref('/log/{pushId}/original')
.onWrite((change,context)=>{
  let afterSnapshot = change.after;

  // onWrite is triggered on deletion
  if (!afterSnapshot.exists()) {
    console.log('cancelled: entry deleted');
    return; // do nothing (could also delete /log/:pushId/uppercase?)
  }

  // Grab the new value written to the Realtime Database and modify it.
  const newValue = afterSnapshot.val();
  const uppercase = newValue.toUpperCase();

  // Set "../uppercase" and returns its operation Promise.
  return afterSnapshot.ref.parent.child('uppercase').set(uppercase);
});

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