傳遞迴調函數，以貓鼬聚合函數

Question

我形成了查詢內聚集（）如下執行：

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，當我執行以下命令：

DataTable.aggregate(query); 

我得到這樣的：

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 

我現在二人的問題：

• 有沒有更好的方式來形成這個查詢。
• 如何在這裏指定回調函數。

編輯

我修改上面的代碼如下：

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，當我執行以下：

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

Answer 1

引用Mongoose's documentation for aggregate，

個參數：

1. [...] <Object, Array>聚集管道運營商（S）或運營商陣列

2. [callback] <Function>

它期待你傳遞

1. 聚合管道運營商

   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. 或多個聚合管道運營商作爲單獨的參數

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

我寧願管道建設者的方式傳遞的數組，

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) { 

}); 

編輯：如果你喜歡單獨編制單個項目，那麼你可以使用數組對象，這樣

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) { 

}); 

或者使用管道建設者，

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

});