async.each嵌套在async.waterfall

我最近開始使用異步api。現在我的要求是對3個集合（即字段，腳本和語句）執行加入。字段可以有多個腳本，腳本可以有多個語句。async.each嵌套在async.waterfall

這裏是我到目前爲止已經試過：（加盟Fields集合使用腳本）

// Array to hold async tasks 
var asyncTasks = []; 

async.waterfall([ 
    function(callback){ 
     // fetches fields based on some Id and it returns 2 fields 
     db.fields.find({entity_id: mongojs.ObjectId("54440a448bbbcbb4070131ab")}, function (err, fields) { 
      console.log(JSON.stringify(fields, null, 2)); 
      callback(null, fields); 
     }) 
    }, 
    function(arg1, callback){ 
     // arg1 now equals fields   
     arg1.forEach(function(eachField){ 
      asyncTasks.push(function(callback){ 
       db.scripts.find({fieldId: eachField._id.valueOf()}, function(err, scripts) { 
        // Async call is done then alert via callback 
        console.log(JSON.stringify(scripts, null, 2)); 
        callback(null, scripts); 
       }); 
      }); 
     }); 


     // Now we have an array of functions doing async tasks 
     // Execute all async tasks in the asyncTasks array 
     async.parallel(asyncTasks, function(err, results) { 
      // All tasks are done now 
      console.log("Scripts" + JSON.stringify(results, null, 2)); 
      callback(null, "done"); 
     }); 

    } 
], function (err, result) { 
     console.log(result); 
});

// for the above code here is what i get the output 
[ 
    { 
    "_id": "54440a548bbbcbb4070131ac", 
    "name": "t1", 
    "type": "String", 
    "entity_id": "54440a448bbbcbb4070131ab" 
    }, 
    { 
    "_id": "54447f1d20c103981fa1a27c", 
    "name": "t2", 
    "type": "String", 
    "entity_id": "54440a448bbbcbb4070131ab" 
    } 
] 
size of array 2 
[] 
[] 
Scripts[ 
    [], 
    [] 
] 
done

以上輸出不打印任何腳本，即使有數據庫中有2個腳本。我的數據庫位於MongoDB中，我正在使用NodeJs和MongoJS api。爲什麼db.scripts.find（）返回空數組？任何幫助表示讚賞

我測試了這段代碼，看看腳本返回o/p。請在下面找到我的代碼

test2(); 
    function test2(){ 

     var getScriptFunction = function(eachField, doneCallback){ 
      if(eachField !== undefined) { 
       var fieldId = eachField; 
       console.log(fieldId); 
       db.scripts.find({fieldId: fieldId}, function (err, result) { 
        // Async call is done, alert via callback 
        doneCallback(null, result); 
       }); 
      } 
     } 
     // The array is the id of fields 
     async.map(["54440a548bbbcbb4070131ac", "54447f1d20c103981fa1a27c"], getScriptFunction, function (err, results) { 
      // Square has been called on each of the numbers 
      // so we're now done! 
      if (err){ 
       console.log("error!" + err); 
      } else { 
       console.log("printed from helper function \n" + JSON.stringify(results, null, 2)); 
      } 
     }); 
    }

這是上面的代碼的O/P獲取腳本單獨

printed from helper function 
[ 
    [ 
    { 
     "_id": "54440a678bbbcbb4070131ad", 
     "name": "s1", 
     "fieldId": "54440a548bbbcbb4070131ac" 
    }, 
    { 
     "_id": "544af260eb7a486824a5c306", 
     "name": "s2", 
     "fieldId": "54440a548bbbcbb4070131ac" 
    } 
    ], 
    [] 
]

這是場什麼樣子（db.fields跑.find（）。pretty（））

[ 
    { 
    "_id": "54440a548bbbcbb4070131ac", 
    "name": "t1", 
    "type": "String", 
    "entity_id": "54440a448bbbcbb4070131ab" 
    }, 
    { 
    "_id": "54447f1d20c103981fa1a27c", 
    "name": "t2", 
    "type": "String", 
    "entity_id": "54440a448bbbcbb4070131ab" 
    } 
]

來源

2014-11-06 maddyeng

試着將'eachField._id'直接放在你的find查詢中，而不是'eachField._id.valueOf（）'。如果你給它一個真正的ObjectId實例，查詢只會匹配正確。 – 2014-11-06 10:52:23

它不會工作，因爲fieldId被保存爲字符串值而不是ObjectId。 – maddyeng 2014-11-06 16:19:37

我嘗試了你的建議，但仍然沒有運氣 – maddyeng 2014-11-06 16:36:25

我能解決問題。有兩個問題（1）我的回調函數名稱相同，即內部和外部回調嵌套在一起。（2）我必須使用toString（）而不是valueOf（）

來源

2014-11-07 22:33:11 maddyeng

async.each嵌套在async.waterfall

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