将查找查询中的结果猫鼬返回给变量 [英] Return results mongoose in find query to a variable

问题描述

我需要在node.js中用猫鼬返回查询结果.

I need to return the results of a query with mongoose in node.js.

如何返回值以将值设置为变量?

How do you return the value to set the value to a variable?

我需要做的是:

var results = users.findOne({_id : users_list[i]['user_id']},{email : 1, credits : 1},{}, function(err, docs) {
    if( err || !docs) {
        console.log("No user found");
    } else {            
        return docs;
    };
});

要拥有:

results = docs 

非常感谢您的答复.

我还有另一个问题.

如何使用find或findOne在查询运算符中传递变量?像:

How to pass variable in a query operator with find or findOne? Like :

var foo = "Blaa";

users.findOne({_id : users_list[i]['user_id']},{email : 1, credits : 1},{}, function(err, docs) {
    if( err || !docs) {
        console.log("No user found");
    } else {
        // I want to use the foo variable here
        console.log(foo);
    };
});

推荐答案

有几种方法可以实现所需的目标.

There are several ways to achieve what you want.

1.使用猫鼬查询

在这种策略中，您的函数返回一个Mongoose查询，您以后可以使用该查询来调用方法exec并使用它来获取结果.

In this strategy, your function returns a Mongoose query which you can later use to invoke the method exec and use it to get the results.

function getJedisQuery(name){
   var query = Jedi.find({name:name});
   return query;
}

然后您可以简单地使用它:

Then you can use it simply doing:

var query =  getJedisQuery('Obi-wan');
query.exec(function(err,jedis){
   if(err)
      return console.log(err);
   jedis.forEach(function(jedi){
      console.log(jedi.name);
   });
});

2.使用类似猫鼬的诺言对象

Moogose为类似诺言的对象提供支持.您所要做的只是与我上面所做的类似，但是这次，您调用了exec方法而没有回调.

Moogose provides support for promise-like objects. All you have to do is something somewhat similar to what I did above, but this time, you invoke the exec method without a callback.

function getJedisPromise(name){
   var promise = Jedi.find({name:name}).exec();
   return promise;
}

然后您可以通过简单的操作来使用它:

Then you can use it by simply doing:

var promise = getJedisPromise('Luke');
promise.then(function(jedis){
   jedis.forEach(function(jedi){
      console.log(jedi.name);
   });
})

正如该答案的注释部分中突出显示的那样，这些对象实际上不是承诺，需要考虑在内(请参阅

As highlighted in the comment section of this answer, these objects are not in fact promises and that needs to be taken into account (see Queries are not promises).

3.使用猫鼬流

最后，猫鼬还支持流，并且流是事件发射器.因此，您可以获取流，然后订阅数据"和错误"事件.像这样:

Finally, Mongoose has also support for streams and streams are event emitters. So, you could get a stream and then subscribe for 'data' and 'error' events. Like this:

function getjedisStream(name){
   var stream = Jedi.find({name:name}).stream();
   return stream;
}

然后您可以简单地进行以下操作:

Then you can simply do:

var stream = getJedisStream('Anakin');
stream.on('data', function(jedis){
   jedis.forEach(function(jedi){
      console.log(jedi.name);
   });
});
stream.on('error', function(error){
    console.log(error);
});

来源，以供将来参考.

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