将回调函数传递给mongoose聚合函数

时间:2015-02-08 04:54:50

标签: javascript node.js mongodb mongoose

我正在形成要在aggregate()中执行的查询,如下所示:

query.$project = {};
query.$project.created_at = '$created_at';
query.$project.month = {};
query.$project.month.$month = currentMonth;
query.$match = {};
query.$match.month = currentMonth.getMonth() + 1;
query.$limit = 5;
query.$sort = {};
query.$sort.created_at = -1;
query.callback = function(err, result){
    // do something
};
console.dir(query);

但是当我执行以下内容时:

DataTable.aggregate(query);

我明白了:

Error: Arguments must be aggregate pipeline operators
    at Aggregate.append (C:\myproject\node_modules\mongoose\lib\aggregate.js:87:11)
    at new Aggregate (C:\myproject\node_modules\mongoose\lib\aggregate.js:47:17)
    at Function.aggregate (C:\myproject\node_modules\mongoose\lib\model.js:1889:17)
    at C:\myproject\app\routes.js:179:23
    at C:\myproject\node_modules\async\lib\async.js:570:21
    at C:\myproject\node_modules\async\lib\async.js:249:17
    at C:\myproject\node_modules\async\lib\async.js:125:13

我现在有两个问题:

  • 是否有更好的方法来形成此查询。
  • 我如何在这里指定回调函数。

修改

我修改了上面的代码如下:

query.$project = {};
query.$project.created_at = '$created_at';
query.$project.month = {};
query.$project.month.$month = currentMonth;
query.$match = {};
query.$match.month = currentMonth.getMonth() + 1;
query.$limit = 5;
query.$sort = {};
query.$sort.created_at = -1;

但是当我执行以下内容时:

DataTable.aggregate(query, function(err, result){
    // do something
});

1 个答案:

答案 0 :(得分:7)

引用Mongoose's documentation for aggregate

  

<强>参数:

     
      
  1. [...] <Object, Array>聚合管道运算符或运算符数组

  2.   
  3. [callback] <Function>

  4.   

期待你通过

  1. 聚合管道运算符数组

    DataTable.aggregate([{
        $project: {
            created_at: '$created_at',
            month: {
                $month: currentMonth
            }
        }
    }, {
        $match: {
            month: currentMonth.getMonth() + 1
        }
    }, {
        $limit: 5
    }, {
        $sort: {
            created_at: -1
        }
    }], function(err, result) {
    
    });
    
  2. 或多个聚合管道运算符作为单独的参数传递

    DataTable.aggregate({
        $project: {
            created_at: '$created_at',
            month: {
                $month: currentMonth
            }
        }
    }, {
        $match: {
            month: currentMonth.getMonth() + 1
        }
    }, {
        $limit: 5
    }, {
        $sort: {
            created_at: -1
        }
    }, function(err, result) {
    
    });
    
  3. 我更喜欢管道构建器方式,

    DataTable.aggregate().project({
        created_at: '$created_at',
        month: {
            $month: currentMonth
        }
    }).match({
        month: currentMonth.getMonth() + 1
    }).limit(5).sort({
        created_at: -1
    }).exec(function(err, result) {
    
    });
    

    编辑:如果您更喜欢单独准备单个项目,那么您可以使用数组对象,例如

    var query = [];
    
    query.push({
        $project: {
            created_at: '$created_at',
            month: {
                $month: currentMonth
            }
        }
    });
    
    query.push({
        $match: {
            month: currentMonth.getMonth() + 1
        }
    });
    
    query.push({
        $limit: 5
    });
    
    query.push({
        $sort: {
            created_at: -1
        }
    });
    
    DataTable.aggregate(query, function(err, result) {
    
    });
    

    或使用管道构建器

    var aggregator = DataTable.aggregate();
    ...
    aggregator = aggregator.project({...});
    ...
    aggregator = aggregator.match({...});
    ...
    aggregator = aggregator.limit(...);
    ...
    aggregator = aggregator.sort(...);
    ...
    aggregator.exec(function(err, result) {
    
    });