Async.waterfall函数被调用两次

Question

I have an async waterfall Array where the function otherIngrLists() is the 3rd to be executed. Every function before that worked fine.

function otherIngrLists(userslist, callback){
    collection = db.get('ingrList');
    collection.find({"userid":{$ne:userid}},{},function(err,docs){ 
      if(!err){
        var otherLists = docs;
        var otherListsCount = docs.count();
        console.log(otherListsCount);
        callback(null, otherLists, otherListsCount, userslist);
      } else {
          callback(err, null);
      }
   });
 },

The Problem is that this function is called twice. I assured this with a simple console.log().

How did I manage to call this function again? Did I get the concept of callbacks wrong as I use them to be passed on to the next function?

Also after this function executing twice an error ist thrown. It has nothing to to with this problem though and I will concern my self with that later. Thank you for your time!

Waterfall Array in router.get:

router.get('/:userid', function(req, res) {
  var db = req.db;
  var collection;
  var userid = req.params.userid;

  async.waterfall(
[
  function getIngrList(callback, userid) {
    var route = 'http://localhost:3000/users/zutatenliste/'+userid;

    request(route, function(err, response, body){
      if (!err && response.statusCode === 200) {
        var userlist = body;
        callback(null, userlist);
      } else {
        callback(err, null);
        return;
      }
    });
  },

  function otherIngrLists(userlist, callback){
    collection = db.get('zutatenListe');
    console.log(userid);
    collection.find({"userid":{$ne:userid}},{},function(err,docs){  
      if(!err){
        var otherLists = docs;
        var otherListsCount = docs.count();
        callback(null, otherLists, otherListsCount, userlist);
      } else {
        callback(err, null);
      }
    });
  },

  function pushInArray(otherLists, otherListsCount, userlist, callback){
    console.log("test");
    ...
    ...}
     }
   }

Edit 1: --Also either if cases are executed, first the true one then the false-- // Does not happen anymore

Edit 2: Added the whole Thing until the problematic function

Answer 1

Please provide some Additional details as this function seems perfect and No, You haven't misunderstood the concept of callback you are using it correctly.

Structure of Async Waterfall

var create = function (req, res) {
        async.waterfall([
            _function1(req),
            _function2,
            _function3
        ], function (error, success) {
            if (error) { alert('Something is wrong!'); }
            return alert('Done!');
        });
    };

    function _function1 (req) {
        return function (callback) {
            var something = req.body;
            callback (null, something);
       }
    }

    function _function2 (something, callback) {
        return function (callback) {
           var somethingelse = function () { // do something here };
           callback (err, somethingelse);
        }
    }

    function _function3 (something, callback) {
        return function (callback) {
          var somethingmore = function () { // do something here };
          callback (err, somethingmore);
        }
   }

so, in waterfall you can pass the values to the next function and your 3rd function is correct.

Edited

  async.waterfall(
[
    //can not give userId as second parameter
  function getIngrList(callback) {
      //if you want userId you can pass as I shown above or directly use here if it's accessible
    var route = 'http://localhost:3000/users/zutatenliste/'+userid;

    request(route, function(err, response, body){
      if (!err && response.statusCode === 200) {
        var userlist = body;
        callback(null, userlist);
      } else {
        callback(err, null);
        // return; no need
      }
    });
  },

  function otherIngrLists(userlist, callback){
    collection = db.get('zutatenListe');
    console.log(userid);
    collection.find({"userid":{$ne:userid}},{},function(err,docs){  
      if(!err){
        var otherLists = docs;
        var otherListsCount = docs.count();
        callback(null, otherLists, otherListsCount, userlist);
      } else {
        callback(err, null);
      }
    });
  },

  function pushInArray(otherLists, otherListsCount, userlist, callback){
    console.log("test");
    ...
    ...}

As said you can not pass userId as last parameter over there. Let me know if you still get the same error.

Answer 2

First you need to declare you function:

function myFuntion(userId, callback) {
    async.waterfall([

        function(callback) {
            //do some thing here
            callback(null, userlist);
        }, function(userId, callback) {
            //do something here
            callback(null, orderList, orderListCount, userlist);
        }

    ], function(err, orderList, orderListCount, userlist) {
        if(err)
           console.log(err);
        else
           callback(orderList, orderList, userlist);
    })
}

After that you can use function:

myFuntion(userId, function(orderList, orderListCount, userlist) {

    console.log(orderList);
    console.log(orderListCount);
    console.log(userlist);
})