使用Firebase-util连接表时未正确触发的火基事件

Question

我使用Firebase-util的交集函数来查找给定链接的所有注释。这在我第一次调用join时似乎运行良好，但当我删除数据库的内容并再次替换它们时，它似乎没有正确地通知我的值回调。只要资源路径保持不变，引用就不应该继续工作吗？

运行此示例。单击该按钮时，它会擦除和重新创建数据。如您所见，在重新创建数据之后，不会重新填充注释列表。

<link rel="import" href="https://www.polymer-project.org/components/polymer/polymer.html">

<script src="http://cdn.firebase.com/v0/firebase.js"></script>
<script src="https://cdn.firebase.com/libs/firebase-util/0.1.0/firebase-util.min.js"></script>

<polymer-element name="my-element">
  <template>
    <h1>Test of Firebase-util.intersection</h1>
    <div>
      <button on-click={{initializeFirebase}}>Reset data</button>
    </div>
    <ul>
      <template repeat="{{rootComment in comments}}">
        <li>{{rootComment.comment.content}}
          <ul>
            <template repeat="{{subComment in rootComment.children}}">
              <li>{{subComment.comment.content}}
                <ul>
                  <template repeat="{{subSubComment in subComment.children}}">
                    <li>{{subSubComment.comment.content}}</li>
                  </template>
                </ul>
              </li>
            </template>
          </ul>
        </li>
      </template>
    </ul>
  </template>
  <script>
    Polymer('my-element', {
      ready: function() {
        var sanitizeUrl = function(url) {
          return encodeURIComponent(url).replace(/\./g, '%ZZ');
        };
        var baseUrl = "https://nested-comments-test.firebaseio.com";
        var linkUrl = baseUrl +
          '/links/' +
          sanitizeUrl(document.URL) +
          '/comments';
        var commentsUrl = baseUrl + '/comments';
        var root = new Firebase(baseUrl);

        this.initializeFirebase = function() {
          function addLink(url, callback) {
            var key = sanitizeUrl(url),
              newLink = {
                url: url,
                createdAt: Firebase.ServerValue.TIMESTAMP
              };
            root.child('/links/' + key).update(newLink);
            callback(key);
          }

          function addComment(attributes, callback) {
            return root.child('/comments').push(attributes, callback);
          }

          function onCommentAdded(childSnapshot) {
            var newCommentId = childSnapshot.name(),
              attributes = {},
              link = childSnapshot.val().link,
              url = '/links/' + link + '/comments';
            attributes[newCommentId] = true;
            root.child(url).update(attributes);
          }

          root.remove(function() {
            root.child('/comments').on('child_added', onCommentAdded);
            addLink(document.URL, function(link) {
              var attributes = {
                  link: link,
                  content: "This is the first comment."
                },
                firstCommentId, secondCommentId;
              firstCommentId = addComment(attributes).name();
              attributes = {
                link: link,
                content: "This is a reply to the first.",
                replyToCommentId: firstCommentId
              };
              secondCommentId = addComment(attributes).name();
              attributes = {
                link: link,
                content: "This is a reply to the second.",
                replyToCommentId: secondCommentId
              };
              addComment(attributes);
              attributes = {
                link: link,
                content: "This is another reply to the first.",
                replyToCommentId: firstCommentId
              };
              addComment(attributes);
            });
          });
        };
        this.initializeFirebase();

        var findChildrenForComment = function(snapshot, parentCommentId) {
          var returnVal = [];
          snapshot.forEach(function(snap) {
            var comment = snap.val(),
              commentId = snap.name();
            if (comment.replyToCommentId === parentCommentId) {
              var children = findChildrenForComment(snapshot, commentId);
              var obj = {
                commentId: commentId,
                comment: comment,
                parentId: parentCommentId
              };
              if (children.length) {
                obj.children = children;
              }
              returnVal.push(obj);
            }
          });
          return returnVal;
        };

        this.ref = Firebase.util.intersection(
          new Firebase(linkUrl),
          new Firebase(commentsUrl)
        );
        this.comments = {};
        var that = this;
        this.ref.on('value', function(snapshot) {
          that.comments = findChildrenForComment(snapshot);
        });
      }
    });
  </script>
</polymer-element>
<my-element></my-element>

Answer 1

显然，完全删除路径会导致其上的所有回调被取消。此行为的解决方法是一次删除一个子路径，而不是删除其父路径。