René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"FirebaseListObservables retrieve the initial list content twice","articleBody":"\u003c!--\r\n\r\nIMPORTANT! YOU MUST FOLLOW THESE INSTRUCTIONS OR YOUR ISSUE WILL BE CLOSED.\r\n\r\nThank you for contributing to the Firebase community!\r\n\r\nHave a usage question?\r\n=======================\r\nWe get lots of those and we love helping you, but GitHub is not the best place for them and they\r\nwill be closed. Here are some resources to get help:\r\n\r\n- Start with the README: https://github.com/angular/angularfire2\r\n- Go through the Developer's Guide: https://github.com/angular/angularfire2#developer-guide\r\n- Read the full API reference: https://github.com/angular/angularfire2/blob/master/docs/api-reference.md\r\n\r\nIf the official documentation doesn't help, try asking through our officially supported channels:\r\n\r\n- Angular Google Group: https://groups.google.com/forum/#!forum/angular\r\n- Firebase Google Group: https://groups.google.com/forum/#!forum/firebase-talk\r\n- Stack Overflow: https://stackoverflow.com/questions/tagged/angular (include the firebase and angularfire tags, too!)\r\n\r\n*Please avoid double posting across multiple channels!*\r\n\r\nThink you found a bug?\r\n=======================\r\nYeah, we're definitely not perfect! Please use the bug report template below and include a minimal\r\nrepro when opening the issue.\r\n\r\nHave a feature request?\r\n========================\r\nGreat, we love hearing how we can improve our products! Remove the template below and\r\nprovide an explanation of your feature request. Provide code samples if applicable. Try to\r\nthink about what it will allow you to do that you can't do today? How will it make current\r\nworkarounds straightforward? What potential bugs and edge cases does it help to avoid?\r\n\r\n--\u003e\r\n\r\n\r\n### Version info\r\n\r\n\u003c!-- What versions of the following libraries are you using? Note that your issue may already\r\nbe fixed in the latest versions. --\u003e\r\n\r\n**Angular:** 2.4.7\r\n**Firebase:** 3.6.9\r\n**AngularFire:** 2.0.0-beta.7\r\n**Other (e.g. Ionic/Cordova, Node, browser, operating system):** N/A\r\n\r\n### How to reproduce these conditions\r\n\r\n**Failing test unit, Plunkr, or JSFiddle demonstrating the problem**\r\n\r\nThere is a plunk [here](https://plnkr.co/edit/ByZmgLYXQkzymmc18RhF).\r\n\r\n**Steps to set up and reproduce**\r\n\r\nOpen the above plunk and then:\r\n\r\n* Open the Dev Tools and go to the Network tab.\r\n* Select WS or All to observe the WebSocket traffic.\r\n* Run the plunk.\r\n* There will be an entry of about 7557 bytes which is the initial content written to the database.\r\n* That entry will be followed by *two* of about 7550 bytes and those entries are the content thats read from the database.\r\n\r\nThe problem is caused by `on('child_added', ...)` not being called until *after* the `on('value')` promise has resolved.\r\n\r\n### Expected behavior\r\n\r\nWhen subscribing to a `FirebaseListObservable` that has content that exists in the database, a single copy of the content should be retrieved across the network.\r\n\r\n### Actual behavior\r\n\r\nTwo copies of the content are retrieved across the network.","author":{"url":"https://github.com/cartant","@type":"Person","name":"cartant"},"datePublished":"2017-02-10T03:08:19.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/819/angularfire/issues/819"}