Question

我正在尝试在添加新消息时通过Firebase Cloud Functions向组的每个成员发送推送通知。我不习惯使用Promises，在这里需要一些帮助。

exports.sendPushFromMessage = functions.database.ref('chats/{groupId}/messages/{msgId}').onCreate((snap, context) => {
    const groupId = context.params.groupId;
    const users = [];
    const msgTitle = 'New Message';
    const msgBody = snap.val().messageText;
    const creator = snap.val().from;
    const root = snap.ref.root;
    let messages = [];
    return root.child(`groups/${groupId}/selected`).once('value', snapshot => {
      snapshot.forEach(user => {
        root.child(`users/${user.val().uid}`).once('value', spanshot => {
          const expoToken = snapshot.val().token;
          const userId = snapshot.val().uid;
          if (expoToken && (creator !== userId)) {
            messages.push({
              "to": expoToken,
              "title": msgTitle,
              "body": msgBody
            });
          }
        })
      })
      return messages;
    }).then(messages => {
      return fetch('https://exp.host/--/api/v2/push/send', {
        method: "POST",
        headers: {
            "Accept": "application/json",
            "Content-Type": "application/json"
        },
        body: JSON.stringify(messages)
      })
    }).catch((e) => console.log(e));
  })

在Firebase函数的日志中，我看到以下错误：

函数返回了未定义的预期承诺或值

我知道问题可能在于我如何处理Promises。这个问题困扰了我很长一段时间，如果有人可以帮助我，那真是太棒了。

这是我尝试过的另一种方法：

exports.sendPushFromMessage = functions.database.ref('chats/{groupId}/messages/{msgId}').onCreate((snap, context) => {
    const groupId = context.params.groupId;
    const users = [];
    const msgTitle = 'New Message';
    const msgBody = snap.val().messageText;
    const creator = snap.val().from;
    const root = snap.ref.root;
    root.child(`groups/${groupId}/selected`).once('value', snapshot => {
      let users = [];
      snapshot.forEach(user => {
        const uid = user.val().uid;
        users.push(uid);
        console.log('fotze' + user.val().uid);
      })
      return Promise.all(users);
    })
    .then(users => {
      let messages = [];
      console.log(users);
      users.forEach(user => {
        console.log('fucking bitch: ' + user.toString());
        console.log('bitch!' + user);
        root.child(`users/${user}/`).once('value', snapshot => {
          const expoToken = snapshot.val().token;
          const userId = snapshot.val().uid;
          console.log('cunt' + snapshot.val().token);
          if (expoToken && (creator !== userId)) {
            messages.push({
                "to": expoToken,
                "title": msgTitle,
                "body": msgBody
            })
          } // if
        }); // once
      }); //forEach
      return Promise.all(messages);
    })
    .then(messages => {
      return fetch('https://exp.host/--/api/v2/push/send', {
        method: "POST",
        headers: {
            "Accept": "application/json",
            "Content-Type": "application/json"
        },
        body: JSON.stringify(messages)
      })
    }).catch((e) => console.log(e));
  })

Answer 1

请以这种方式进行测试：

exports.sendPushFromMessage = functions.database.ref('chats/{groupId}/messages/{msgId}').onCreate((snap, context) => {
  const groupId = context.params.groupId;
  const users = [];
  const msgTitle = 'New Message';
  const msgBody = snap.val().messageText;
  const creator = snap.val().from;
  const root = snap.ref.root;
  let messages = [];
  const promises = [];
  return root.child(`groups/${groupId}/selected`).once('value', snapshot => {
    snapshot.forEach(user => {
      const promise = root.child(`users/${user.val().uid}`).once('value', snapshot => {
        const expoToken = snapshot.val().token;
        const userId = snapshot.val().uid;
        if (expoToken && (creator !== userId)) {
          messages.push({
            "to": expoToken,
            "title": msgTitle,
            "body": msgBody
          });
        }
      });
      promises.push(promise);
    });
    return Promise.all(promises).then(() => {
      return sendMessages(messages);
    });
  });
});

function sendMessages(messages){
  return new Promise((resolve, reject) => {
    const f = fetch('https://exp.host/--/api/v2/push/send', {
      method: "POST",
      headers: {
        "Accept": "application/json",
        "Content-Type": "application/json"
      },
      body: JSON.stringify(messages)
    });
    f.on("end", () => {
      resolve();
    });
  });
}

Firebase云函数“函数返回的值未定义，预期的承诺或价值”

1 个答案: