Question

我最近开始使用async api。现在我的要求是在3个集合上执行连接即字段，脚本和语句。字段可以有多个脚本，脚本可以有多个语句。

这是我到目前为止所尝试的内容:(使用脚本加入Fields集合）

// 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

即使数据库中有2个脚本，上述输出也不会打印任何脚本。我的数据库是在MongoDB中，我使用的是NodeJs，MongoJS api。为什么db.scripts.find（）返回空数组？任何帮助表示赞赏

我测试了这段代码，看看脚本是否返回o / p。请在下面找到我的代码

 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));
            }
        });
    }

这是上面提取脚本单独运行的代码的o / p

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

这是字段的样子（db.fields.find（）。pretty（））

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

Answer 1

我能够解决问题。有2个问题（1）我的回调函数名称相同，即内部和外部回调嵌套在彼此之内。（2）我不得不使用toString（）而不是valueOf（）

async.each嵌套在async.waterfall中

1 个答案: