在 Meteor Mongo 中寻找价值 [英] Find Value in Meteor Mongo

问题描述

我是网络编程的新手，最近一直在玩 Meteor 和 MongoDB.

I am new to web programming and have recently been playing around with Meteor and MongoDB.

我有一个向 mongo 发送数据的表单，并使用下面的查询检索了最近输入的值:

I have a form which sends data to mongo and using the query below have retrieved the most recently entered value:

database.findOne({}, {sort: {'timeStamp' : -1}, limit:1})

不过，这很酷，我只想要特定变量的值而不是整个条目，因此我可以在其他地方使用该变量进行计算.

Which is cool however, I only want the value of a specific variable not the entire entry so I can use that variable with calculations elsewhere.

有人有专业提示吗?我应该使用 distinct() 吗?

Does anyone have an pro tips? Should I use distinct()?

谢谢！

推荐答案

如果您想从返回的文档中检索字段，您可以使用 fields 选项指定尽可能多的字段:>

If you are looking to retrieve a field out of the returned document, you can specify as much using the fields option:

database.findOne({}, {sort: {'timeStamp' : -1}, limit:1, fields: {'myField': 1, _id: 0})

这将以如下格式检索对象:

That will retrieve an object in format like this:

{'myField': 'value of myField'}

所以如果你想直接与之交互，你可以像这样访问它:

So if you want to interact directly with that you can access it like so:

var myVar = database.findOne({}, {sort: {'timeStamp' : -1}, limit:1, fields: {'myField': 1, _id: 0}).myField

举一个更具体的例子，我有一个包含用户名、名称、_id 等的用户数据库，如果我只想将用户名存储在另一个变量中，我可以这样做:

As a more concrete example, I have a user database with username, name, _id, etc., and if I just want to store a user's name in another variable, I can do so like this:

> a = Meteor.users.findOne({}, {fields: {name: 1, _id: 0}}).name;
> a
<- "Bob" // returned "Bob"

请注意，如果您想为特定 ID 或其他选择器提取数据，则需要在选择器中填写:

Note that if you want to pull the data for a specific ID or other selector, you'll need to fill that in in the selector:

database.findOne({_id: "myId"}, ...)

有关详细信息，请参阅 Meteor Mongo.Collection.find 文档.

See the Meteor Mongo.Collection.find documentation for more information.

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