Firebase Angular 2-防止为每个订阅的客户端刷新观察到的对话列表的方法

所以我利用Angular 2/Firebase observables创建一个用户参与的对话列表。但是，我注意到，如果在

/conversations

端点中更新了任何对话，即使用户不是该对话的一部分，其对话列表的UI也会显示刷新

基本上，我试图弄清楚这是因为所有的对话都在一棵树中，还是我的代码中有什么东西导致了这种情况的发生

无论哪种方式，下面是一个如何设计我的对话树的示例：

/conversations

{
  "-KfOStwLKzERlOxIaU7V" : {
    "created_at" : "2017-03-16T23:32:59.830Z",
    "creator_id" : "dsfsdg12123RSDvsfbgrgwef",
    "last_message" : "helllooo",
    "last_message_author_id" : "dsfsdg12123RSDvsfbgrgwef",
    "last_updated" : "2017-03-16T23:46:05.645Z",
    "type" : "individual",
    "users" : {
      "dsfsdg12123RSDvsfbgrgwef" : true,
      "gHRdadg567AAA344cGHJsaw1" : true
    }
  }
}

{
   "convoId1": true,
   "convoId2": true
}

/users/{userID}/conversations

{
  "-KfOStwLKzERlOxIaU7V" : {
    "created_at" : "2017-03-16T23:32:59.830Z",
    "creator_id" : "dsfsdg12123RSDvsfbgrgwef",
    "last_message" : "helllooo",
    "last_message_author_id" : "dsfsdg12123RSDvsfbgrgwef",
    "last_updated" : "2017-03-16T23:46:05.645Z",
    "type" : "individual",
    "users" : {
      "dsfsdg12123RSDvsfbgrgwef" : true,
      "gHRdadg567AAA344cGHJsaw1" : true
    }
  }
}

{
   "convoId1": true,
   "convoId2": true
}

下面是获取特定用户对话的代码

    getConvosForUser(userId) {

        return this._af.database
          .object(`/social/users/${userId}/conversations`)

          // Switch to the joined observable
          .switchMap((conversations) => {

            // Delete the properties that will throw errors when requesting
            // the convo keys
            delete conversations['$key'];
            delete conversations['$exists'];
            delete conversations['$value'];

            // Get an array of keys from the object returned from Firebase
            let convoKeys = Object.keys(conversations);
            let convosObj = conversations;

            if(convoKeys.length > 0) {
              return Observable.combineLatest(
                convoKeys.map((convoKey) => this._af.database
                  .object(`/social/conversations/${convoKey}`)
                ),
                (...conversations) => {

                  // Determine if the user is connected to the owner
                  convoKeys.forEach(key => {
                    conversations.forEach(conversation => {
                      if(conversation.$key === key) {
                          conversation['is_connected_to_owner'] = convosObj[key];
                      }
                    })
                  })

                  // Then return the aggregated conversation data
                  return conversations;
                }
              );
            // Otherwise, just return an empty observable
            } else {
              return Observable.of([]);
            }
          });
      }

getUsersForConversations(conversations) {

    if(conversations.length > 0) {

      // Since there are conversations, let's iterate
      // over them and determine which to show.
      conversations.forEach((conversation, index) => {
        // Get user out of local storage
        this.storage.get('user').then(user => {

          let userKeys = [];
          // Get the user IDs associated with this conversation
          if(conversation.users) {
            userKeys = Object.keys(conversation.users).filter(key => {
              return key !== user.id;
            });
          }

          let usersArr = [];

          let obsUsers = Observable
            .from(userKeys)
            .flatMap(key => {
              return Observable.combineLatest(
                Observable.of(key),
                this._af.database.object(`/social/conversations_last_deleted/${conversation.$key}/${user.id}`)
                  .filter((lastDeleted) => {
                    let convoLastUpdated = +(new Date(conversation.last_updated));

                    if((lastDeleted && lastDeleted.$value === null) ||
                      (lastDeleted && lastDeleted.last_deleted && (convoLastUpdated >= lastDeleted.last_deleted))) {
                      return true;
                    }
                  })
                  .flatMap(lastDeleted => {
                    return this._messages.getMessagesForConvo(conversation.$key, lastDeleted)
                  }),
                (key, messages) => {
                  if (messages.length === 0) {
                    return null;
                  }
                  return key;
                })
            })
            .flatMap(userKey => this._af.database.object(`/social/users/${userKey}`))
            .subscribe((users) => {

              // There is a weird bug with results returning null,
              // so just check to make sure results aren't null and push
              // the user result if it isn't
              if(users.$value !== null) {
                usersArr.push(users);
                conversations[index].users = usersArr;
                this.conversations = conversations;
              }
            });
        });
      });
    } else {
      return Observable.of([]);
    }
  }

最后是将二者结合在一起的代码：

// Get all of the conversations for a user
      this.convosSub = this._messages.getConvosForUser(user.id).subscribe(conversations => {

        this.usersConvosSub = this.getUsersForConversations(conversations);
      });

我意识到这是很多代码，但我发誓…我的应用程序中的对话部分很容易是最复杂的部分，我已经和它斗争了好几个星期了。我的对话中有很多奇怪的行为，所以我不确定是我的树是如何构造的，还是我的代码是疯狂的

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无论如何，我非常感谢您的帮助

目前还没有（高效且简单的）基于AngularFire2的解决方案。这就是我想要重构

FirebaseListObservable

的原因之一。看到了吗？我现在有点困在这个问题上了吗？是的，在AngularFire2提供了一些工具来告诉你列表已经更改，而且哪些项目已经更改、添加或删除之前，你几乎被困在这个问题上了。