MongoDB Aggregation add next document (流星应用)

Question

下面是我的发布函数，它几乎是Average Aggregation Queries in Meteor的副本

用途:显示文档列表。然后，用户可以单击一个项目(餐厅)，并可以查看详细信息。在详细信息中，有上一个和下一个箭头，这将允许循环通过列表。

我的想法是使用聚合方法来用上一个和下一个文档id来丰富每个文档，这样我就可以轻松地构建我的上一个和下一个链接。

但是怎么做呢？我没有头绪。也许有更好的方法？

Meteor.publish("restaurants", function(coords, options) {
    if (coords == undefined) {
        return false;
    }
    if (options == undefined) {
        options = {};
    }
    if (options.num == undefined) {
        options.num = 4
    }
    console.log(options)
    /**
     * the following code is from https://stackoverflow.com/questions/18520567/average-aggregation-queries-in-meteor
     * Awesome piece!!!
     * 
     * */
    var self = this;
    // This works for Meteor 1.0
    var db = MongoInternals.defaultRemoteCollectionDriver().mongo.db;

    // Your arguments to Mongo's aggregation. Make these however you want.
    var pipeline = [
        {
         $geoNear: {
            near: { type: "Point", coordinates: [ coords.lng , coords.lat ] },
            distanceField: "dist.calculated",
            includeLocs: "dist.location",
            num: options.num,
            spherical: true
         }
       }
    ];

    db.collection("restaurants").aggregate(        
        pipeline,
        // Need to wrap the callback so it gets called in a Fiber.
        Meteor.bindEnvironment(
            function(err, result) {
                // Add each of the results to the subscription.
                _.each(result, function(e) {
                    e.dist.calculated = Math.round(e.dist.calculated/3959/0.62137*10)/10;
                    self.added("restaurants", e._id, e);
                });
                self.ready();
            },
            function(error) {
                Meteor._debug( "Error doing aggregation: " + error);
            }
        )
    );
});

Answer 1

如果你没有太多关于结果的文档，你可以用JavaScript来实现。将您的订阅代码更改为类似这样的代码(我没有测试此代码)。

_.each(result, function(e, idx) {
  if(result[idx - 1]) e.prev = result[idx - 1]._id;
  if(result[idx + 1]) e.next = result[idx + 1]._id;
  e.dist.calculated = Math.round(e.dist.calculated/3959/0.62137*10)/10;
  self.added("restaurants", e._id, e);
});