Steroids/Supersonic with Parse handling data relationships

Question

I ma developing an app with Steroids/Supersonic using Parse as back-end and I am struggling to make object relationships work. Here an example. I have one class Course and one class Teacher with a one to one relationship (each Course one Teacher). What I would like to do is to display all the courses with the associated teacher. To set up the relationship in Parse I have used a column type "Pointer" to the other class. Below the code in the controller:

Course.findAll().then( function (courses) {
        $scope.$apply( function () {
          $scope.courses= courses;

          for (i = 0; i < $scope.courses.length; i++) {
          // look for the teacher
         Teacher.find($scope.courses[i].Teacher.objectId).then( function (teacher) {
            $scope.$apply( function () {
              $scope.courses[i].Teacher= teacher;
            }); 
          });   
          }
        });
      });

The problem of the above code is that the variable "i" is not defined inside the Teacher.find() function so I cannot assign the teacher object to the correct course object. I even tried to use a specific variable in the scope to manage the index as in this other code:

Course.findAll().then( function (courses) {
        $scope.$apply( function () {
          $scope.courses= courses;
          $scope.index = 0
          for (i = 0; i < $scope.courses.length; i++) {
          // look for the teacher
         Teacher.find($scope.courses[i].Teacher.objectId).then( function (teacher) {
            $scope.$apply( function () {
              $scope.courses[$scope.index].Teacher= teacher;
              $scope.index = $scope.index + 1
            }); 
          });   
          }
        });
      });

The problem of this second code is that randomly a teacher is linked to the wrong course maybe because the function find() is called asynchronous so the two variables i and index are not always synchronized.

I believe the problem I am facing is more related to the asynchronous behavior of angularjs but I don't really know how to solve it. Thanks for your help!

I am looking into getting related data like you do with Course and Teacher, but I can't find any documentation on that. How do you get the Teacher object in your Course controller? In the constructor somehow, or what? Thanks in advance — Niklas Wulff, Nov 01 '15 at 02:01

score 0 · Answer 1 · answered Nov 02 '15 at 13:10

I haven't tested this at all, but trying to look at the closures, I could imagine this would work.

Course.findAll().then( function (courses) {
        $scope.$apply( function () {
          $scope.courses= courses;
          $scope.index = 0
          for (i = 0; i < $scope.courses.length; i++) {
              // look for the teacher
              var course = $scope.courses[i]; // to keep available in closure
         Teacher.find(course.Teacher.objectId).then( function (course, teacher) {
            $scope.$apply( function () {
              course.Teacher= teacher; // course should be available here, due to the closure

            }); 
          });   
          }
        });
      });

Steroids/Supersonic with Parse handling data relationships

1 Answers1