Find multiple random data using promise and recursion

Question

I need to retrieve mutliple random data from my DB.

I have made a service in Sails.js for that purpose.

It's a Recursive function

1. It generate a random number 0 to count of my DB.
2. Stores the random number generated (All questions should be different)
3. Get a random Question
4. Store it in an array calling getQuestion And returning a promise

5. If the random generated array is smaller than the nb Result wanted : We call the function again

    var RandomizerService= {        
         // get a random single question
         // return a promise
         getQuestion: function (limit, skip){
           var dfd = q.defer();
           Question.find().limit(limit).skip(skip).then(function (question){
             dfd.resolve(question);
            });
   
           return dfd.promise;
         },
   
         // Recursive function
         // Generate a random number 0 to count of my DB.
         // Stores the random number generated (All questions should be different)
         // Get a random Question and store it in an array calling getQuestion and returning a promise
         // If the random generated array is smaller than the nb Result wanted : 
         // We call the function again
   
         questions: function (count, tabRes, tabRand, nbRes){
           var dfd = q.defer(); 
           rand = Math.floor(Math.random() * (count - 1)) + 1;
   
           if ( tabRand.indexOf(rand) === -1) {
             tabRand.push(rand);
             RandomizerService.getQuestion(-1, rand).then(function (result){
   
               console.log(result[0]); // Is Returning AFTER the Randomizer.questions called in the Controller
               tabRes.push(result[0]);
               });
             }
             if (tabRand.length<nbRes){
               RandomizerService.questions(count, tabRes, tabRand, nbRes);  
             }
           dfd.resolve(tabRes);
           return dfd.promise;
         }
       };
       module.exports  = RandomizerService;
   

When I'm calling this function in my Controller

RandomizerService.questions(count, [], [], 30).then(function (randQuestions){ 
   console.log(randQuestions);  // Return [];
});

randQuestions in returning an empty array.

But the console.log(result[0]); inside the getQuestions promise is returning AFTER the RandomizerService.questions (in Controller) promise ! oO

(When mocking the find() with a standard promise the whole system works).

Is there a probleme with Waternline or Sails ? What am I doing wrong ?

I'm using Sails.js 0.11 and I use sails.disk but I will use mongDB in the future :)

Thanks guys :)

Answer 1

The first issue is that you're immediately resolving the promise, the second issue is that I think your if statements aren't setup correctly. Try this:

  questions: function (count, tabRes, tabRand, nbRes){
    var dfd = q.defer(); 
    rand = Math.floor(Math.random() * (count - 1)) + 1;

    if ( tabRand.indexOf(rand) === -1) {
      tabRand.push(rand);
      RandomizerService.getQuestion(-1, rand).then(function (result){

        console.log(result[0]); // Is Returning AFTER the Randomizer.questions called in the Controller
        tabRes.push(result[0]);

        if (tabRand.length<nbRes){
          RandomizerService.questions(count, tabRes, tabRand, nbRes)
          .then(function(res){
            dfd.resolve(res);
          })  
        } 
        else {
          dfd.resolve(tabRes);
        }
      });
    } 
    else if (tabRand.length<nbRes){
      RandomizerService.questions(count, tabRes, tabRand, nbRes)
      .then(function(res){
        dfd.resolve(res);
      }) 
    } 
    else {
      dfd.resolve(tabRes);
    }

    return dfd.promise;
  }