将查找查询中的结果猫鼬返回给变量

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(请参阅查询不是保证).

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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