Firebase中的记录总数（我何时计算完？） [英] Total number of records in Firebase (when am I done counting?)

问题描述

计数表中的记录显然是一个手动的努力，直到你们已经在工作中得到一些漂亮的新功能;）

然而，我卡住了甚至使用.on（'value'，...）手动运行来获取计数：

$ $ $ $ $ $ $ $ $ var table =新的Firebase（'http://beta.firebase.com/user/tablename'）;
var count = 0;
table.on（'child_added'，function（snapshot）{
count ++;
//我怎么知道这是否是最后一个孩子？即计数完成？
}）;

//何时可以使用count？

我预见到任何类型的分页都会出现同样的问题，而且我觉得自己有点疯狂对这个。我错过了什么？

这从根本上说是错误的模式，例如获取用户在他/她的队列中的消息数量？ $ b

解决方案

使用child_added，您无法知道何时收到最后一个项目。如果你想要计算在特定时间点所有的孩子，我建议使用价值事件如下：

pre > var table = new Firebase（'http://beta.firebase.com/user/tablename'）;
$ b table.on（'value'，function（snapshot）{
var count = 0;
snapshot.forEach（function（）{
count ++;
}）;
// count现在可以安全的使用。
}）;


Counting records in a table is obviously a manual effort until you guys get some of that spiffy new functionality already in the works ;)

However, I'm stuck on even using a manual run with .on('value', ...) to fetch a count:

var table = new Firebase('http://beta.firebase.com/user/tablename');
var count = 0;
table.on('child_added', function(snapshot) {
   count++;
   // how do I know if this is the last child? i.e. the count is complete?
});

// when is it okay to use count?

I foresee the same issues with any sort of pagination and I feel like I'm being a bit blockheaded about this. What am I missing?

Is this fundamentally the wrong pattern for, say, getting the number of messages a user has in his/her queue?

解决方案

With "child_added" there is no way to know when you've received the "last" item. If you're looking to count all of the children that existed at a particular point in time, I'd suggest using the "value" event as follows:

var table = new Firebase('http://beta.firebase.com/user/tablename');

table.on('value', function(snapshot) {
   var count = 0;
   snapshot.forEach(function() {
       count++;
   });
   //count is now safe to use.
});

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