流星:我怎么知道数据库什么时候准备好了?

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我想在页面加载后尽快执行Meteor集合查询.我尝试的第一件事是这样的:

I want to perform a Meteor collection query as soon as possible after page-load. The first thing I tried was something like this:

Games = new Meteor.Collection("games"); if (Meteor.isClient) { Meteor.startup(function() { console.log(Games.findOne({})); }); }

但是，这不起作用(它显示"undefined").从JavaScript控制台调用该查询后，几秒钟后，该查询就会生效.我认为在数据库准备就绪之前会有些滞后.那么如何知道该查询何时成功?

This doesn't work, though (it prints "undefined"). The same query works a few seconds later when invoked from the JavaScript console. I assume there's some kind of lag before the database is ready. So how can I tell when this query will succeed?

在OSX 10.8和Chrome 25下的流星版本0.5.7(7b1bf062b9).

Meteor version 0.5.7 (7b1bf062b9) under OSX 10.8 and Chrome 25.

推荐答案

您应首先publish来自服务器的数据.

You should first publish the data from the server.

if(Meteor.isServer) { Meteor.publish('default_db_data', function(){ return Games.find({}); }); }

在客户端上，仅在从服务器加载数据之后才执行收集查询.这可以通过在subscribe调用内使用反应式会话来完成.

On the client, perform the collection queries only after the data have been loaded from the server. This can be done by using a reactive session inside the subscribe calls.

if (Meteor.isClient) { Meteor.startup(function() { Session.set('data_loaded', false); }); Meteor.subscribe('default_db_data', function(){ //Set the reactive session as true to indicate that the data have been loaded Session.set('data_loaded', true); }); }

现在，当您执行集合查询时，您可以通过以下方式检查数据是否已加载:

Now when you perform collection queries, you can check if the data is loaded or not as:

if(Session.get('data_loaded')){ Games.find({}); }

注意::删除autopublish程序包，它默认将所有数据发布到客户端，这是不明智的做法.

Note: Remove autopublish package, it publishes all your data by default to the client and is poor practice.

要删除它，请在根项目目录中的每个项目上执行$ meteor remove autopublish.

To remove it, execute $ meteor remove autopublish on every project from the root project directory.