等待 firebase.auth 初始化完成后再执行另一个函数。

huangapple
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英文:

Wait for firebase.auth initialization before reading another function

问题

我对Firebase和JavaScript非常陌生。

我的项目： 构建一个私人消息应用程序。为此，我想在Firestore中定义一个子集合，用于私人消息，使用当前用户的ID和目标用户的ID。

以下是允许这样做的函数：

  1. // 根据当前用户和他试图联系的用户生成正确的子集合
  2. function dmCollection(toUid) {
  4.   if (toUid === null) {
  5.     // 如果没有定义目标用户，我们将其设置为下面的值
  6.     toUid = 'fixed_value';
  7.   };
  8.   const idPair = [firebase.auth().currentUser.uid, toUid].join('_').sort();
  9.   return firebase.firestore().collection('dms').doc(idPair).collection('messages');
  10. };

我的问题： 我想使用firebase.auth().currentUser.uid属性，但似乎该函数不等待firebase.auth初始化。如何解决这个问题？

附加信息：
我有两个调用第一个函数(dmCollection)的函数：

  1. // 检索DM
  2. function messagesWith(uid) {
  3.   return dmCollection(uid).orderBy('sent', 'desc').get();
  4. };
  6. // 发送DM
  7. function sendDM(toUid, messageText) {
  8.   return dmCollection(toUid).add({
  9.     from: firebase.auth().currentUser.uid,
  10.     text: messageText,
  11.     sent: firebase.firestore.FieldValue.serverTimestamp(),
  12.   });
  13. };
英文:

I am very new with firebase and javascript.

My project: Build a private messaging app. To do that, I want to define a sub collection in firestore for private messaging using the current user id and the destination user id.

Here is the function that allows this:

  1. // generate the right SubCollection depending on current User and the User he tries to reach
  2. function dmCollection(toUid) {
  4.   if (toUid === null) {
  5.     // If no destination user is definer, we set it to the below value
  6.     toUid = 'fixed_value';
  7.   };
  8.   const idPair = [firebase.auth().currentUser.uid, toUid].join('_').sort();
  9.   return firebase.firestore().collection('dms').doc(idPair).collection('messages');
  10. };

My problem: I want to use the firebase.auth().currentUser.uid attribute, but it looks like the function is not waiting for firebase.auth initialization. How can I fix this problem?

Additional information:
I have two functions that are calling the first one (dmCollection):

  2. // retrieve DMs
  3. function messagesWith(uid) {
  4.   return dmCollection(uid).orderBy('sent', 'desc').get();
  5. };
  8. // send a DM
  9. function sendDM(toUid, messageText) {
  10.   return dmCollection(toUid).add({
  11.     from: firebase.auth().currentUser.uid,
  12.     text: messageText,
  13.     sent: firebase.firestore.FieldValue.serverTimestamp(),
  14.   });
  15. };

答案1

得分: 2

如果我正确理解您的问题（"看起来函数没有等待firebase.auth初始化"），您有两种可能的解决方案：

解决方案1：在Auth对象上设置观察者

如文档中所解释，您可以使用onAuthStateChanged()方法在Auth对象上设置观察者：

通过使用观察者，您可以确保在获取当前用户时，Auth对象不处于中间状态，例如初始化状态。

因此，您可以将您的代码修改如下：

  1. // 检索DMs
  2. function messagesWith(uid) {
  3.   return dmCollection(uid).orderBy('sent', 'desc').get();
  4. };
  6. // 发送DM
  7. function sendDM(toUid, messageText) {
  8.   return dmCollection(toUid).add({
  9.     from: firebase.auth().currentUser.uid,
  10.     text: messageText,
  11.     sent: firebase.firestore.FieldValue.serverTimestamp(),
  12.   });
  13. };
  15. // 根据当前用户和他尝试联系的用户生成正确的子集合
  16. function dmCollection(toUid) {
  18.   if (toUid === null) {
  19.     // 如果未定义目标用户，我们将其设置为下面的值
  20.     toUid = 'fixed_value';
  21.   };
  22.   const idPair = [firebase.auth().currentUser.uid, toUid].join('_').sort();
  23.   return firebase.firestore().collection('dms').doc(idPair).collection('messages');
  24. };
  26. firebase.auth().onAuthStateChanged(function(user) {
  27.   if (user) {
  28.     var messageText = '....';
  29.     sendDM(user.uid, messageText)
  30.   } else {
  31.     // 没有用户登录。
  32.   }
  33. });

解决方案2：使用currentUser属性

您还可以"使用相同文档中解释的currentUser属性获取当前登录用户"。 "如果用户未登录，currentUser为null"。

在这种情况下，您可以执行以下操作：

  1. var user = firebase.auth().currentUser;
  3. if (user) {
  4.   var messageText = '....';
  5.   sendDM(user.uid, messageText);
  6. } else {
  7.   // 没有用户登录。
  8.   // 提示用户登录，例如重定向到登录页面
  9. }

选择哪种解决方案？

这取决于您希望基于用户的uid何时调用函数：

  • 如果您希望在用户登录后立即调用函数，使用解决方案1。
  • 如果您希望在另一个特定时刻调用函数（例如，按照用户操作），请使用解决方案2。
英文:

If I correctly understand your problem ("it looks like the function is not waiting for firebase.auth initialization"), you have two possible solutions:

###Solution 1: Set an observer on the Auth object###

As explained in the documentation, you can set an observer on the Auth object with the onAuthStateChanged() method:

> By using an observer, you ensure that the Auth object isn't in an
> intermediate state—such as initialization—when you get the current
> user.

So you would modify your code as follows:

  1. // retrieve DMs
  2. function messagesWith(uid) {
  3.   return dmCollection(uid).orderBy('sent', 'desc').get();
  4. };
  7. // send a DM
  8. function sendDM(toUid, messageText) {
  9.   return dmCollection(toUid).add({
  10. 	from: firebase.auth().currentUser.uid,
  11. 	text: messageText,
  12. 	sent: firebase.firestore.FieldValue.serverTimestamp(),
  13.   });
  14. };
  16. // generate the right SubCollection depending on current User and the User he tries to reach
  17. function dmCollection(toUid) {
  19.   if (toUid === null) {
  20. 	// If no destination user is definer, we set it to the below value
  21. 	toUid = 'fixed_value';
  22.   };
  23.   const idPair = [firebase.auth().currentUser.uid, toUid].join('_').sort();
  24.   return firebase.firestore().collection('dms').doc(idPair).collection('messages');
  25. };
  28. firebase.auth().onAuthStateChanged(function(user) {
  29.   if (user) {
  30. 	var messageText = '....';
  31. 	sendDM(user.uid, messageText)
  32.   } else {
  33. 	// No user is signed in.
  34.   }
  35. });

###Solution 2: Use the currentUser property###

You could also "get the currently signed-in user by using the currentUser property" as explained in the same doc. "If a user isn't signed in, currentUser is null".

In this case you would do:

  1. var user = firebase.auth().currentUser;
  3. if (user) {
  4.   var messageText = '....';
  5.   sendDM(user.uid, messageText);
  6. } else {
  7.   // No user is signed in.
  8.   // Ask the user to sign in, e.g. redirect to a sign in page
  9. }

###Which solution to choose?###

It depends how you want to call the function(s) based on the user uid.

  • If you want to call the function(s) immediately after the user is signed in, use Solution 1.
  • If you want to call the function(s) at another specific moment (e.g. following a user action), use Solution 2.

huangapple
  • 本文由 发表于 2020年1月6日 20:23:26
  • 转载请务必保留本文链接：https://go.coder-hub.com/59612070.html
  • firebase
  • google-cloud-firestore
  • google-cloud-platform
  • javascript
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