Updating scope within an iteration in AngularJS

Question

Updating scope within an iteration in AngularJS

I am currently facing an issue with updating subquestions for each question in the code below. Despite my efforts, the subquestions do not update properly and I end up with the same subquestion list for all questions.

How can I display each question along with its corresponding list of subquestions?

  function loadAllQuestionGroup () {
    Questiongroup.query({}).$promise.then(function(group){
        vm.questiongroups = group;
        for(var i=0;i<group.length;i++){
           var grouptitle=group[i].title
            Question.questionsByQuestionGroup({id:group[i].id}).$promise.then(function(question){
                vm.question = question; 
               for(var j=0;j<question.length;j++){    
                  Subquestion.subquestionsByQuestion({id:question[j].id}).$promise.then(function(subquestion){
                      vm.subquestions=subquestion;
                    });                        
              }
         });
        }
      });
    }

 <div ng-repeat="question in vm.question">
   {{question.name}}
   <div ng-repeat="subquestion in vm.subquestions">
     {{subquestion.name}}
   </div>
 </div>

javascript angularjs angularjs-scope angularjs-digest

Answer 1

Answer №1

Seems like the issue at hand is not related to angular scope, but rather with vanilla javascript scope that you seem to be struggling with. If you are making asynchronous calls within a loop, you may find yourself consistently receiving the last element. To resolve this, it's recommended to encapsulate promises inside the loop using anonymous functions.

Consider this common example (you can view the setTimeout function as similar to your

Question.questionsByQuestionGroup({id:group[i].id}).$promise

, as they both represent async operations)

//SIMILAR TO YOUR SITUATION
//This will output the value of 'i' as 5 each time due to closure
for (var i = 0; i < 5; i++) {
  setTimeout(function() {
    console.log(i)
  });
}
//Output: 5 5 5 5 5

//HOW IT SHOULD BE HANDLED
//Encapsulate in a wrapper for proper behavior
for (var j = 0; j < 5; j++) {
  (function(index) {
    setTimeout(function() {
      console.log(index)
    });
  })(j);
}
//Output: 0 1 2 3 4

P.S. Once you implement wrappers to fix this issue, your code might become harder to read, so consider refactoring it into separate functions for better maintainability.

Answer 2

Seems like the issue at hand is not related to angular scope, but rather with vanilla javascript scope that you seem to be struggling with. If you are making asynchronous calls within a loop, you may find yourself consistently receiving the last element. To resolve this, it's recommended to encapsulate promises inside the loop using anonymous functions.

Consider this common example (you can view the setTimeout function as similar to your

Question.questionsByQuestionGroup({id:group[i].id}).$promise

, as they both represent async operations)

//SIMILAR TO YOUR SITUATION
//This will output the value of 'i' as 5 each time due to closure
for (var i = 0; i < 5; i++) {
  setTimeout(function() {
    console.log(i)
  });
}
//Output: 5 5 5 5 5

//HOW IT SHOULD BE HANDLED
//Encapsulate in a wrapper for proper behavior
for (var j = 0; j < 5; j++) {
  (function(index) {
    setTimeout(function() {
      console.log(index)
    });
  })(j);
}
//Output: 0 1 2 3 4

P.S. Once you implement wrappers to fix this issue, your code might become harder to read, so consider refactoring it into separate functions for better maintainability.

Answer 3

Answer №2

Each unique question must be categorized in a question list. A subquestion list should be generated for every individual question. It is necessary to categorize distinct subquestions under their corresponding lists.

function loadAllQuestionGroup () {
    Questiongroup.query({}).$promise.then(function(group){
        vm.questiongroups = group;
        //Set up question list
        vm.questionList = [];
        for (var i=0;i<group.length;i++){
            var grouptitle=group[i].title;
            Question
              .questionsByQuestionGroup({id:group[i].id})
              .$promise
              .then(function(question){
                //Add question to the list
                vm.questionList.push(question); 
                for (var j=0;j<question.length;j++) {
                    //Generate subquestion list
                    question.subquestionList = [];
                    Subquestion
                        .subquestionsByQuestion({id:question[j].id})
                        .$promise
                        .then(function(subquestion){
                             //Add subquestion to the list
                             question.subquestionList.push(subquestion);
                        })
                   ;                        
                };
              })
            ;
        }
    });
}

The iteration of subquestions (ng-repeat) should be done based on the question iterator.

<div ng-repeat="question in vm.questionList">
   {{question.name}}
   <div ng-repeat="subquestion in question.subquestionList">
     {{subquestion.name}}
   </div>
</div>

It's important to note that a subquestionList property has been included in each question within the questionList.

Answer 4

Each unique question must be categorized in a question list. A subquestion list should be generated for every individual question. It is necessary to categorize distinct subquestions under their corresponding lists.

function loadAllQuestionGroup () {
    Questiongroup.query({}).$promise.then(function(group){
        vm.questiongroups = group;
        //Set up question list
        vm.questionList = [];
        for (var i=0;i<group.length;i++){
            var grouptitle=group[i].title;
            Question
              .questionsByQuestionGroup({id:group[i].id})
              .$promise
              .then(function(question){
                //Add question to the list
                vm.questionList.push(question); 
                for (var j=0;j<question.length;j++) {
                    //Generate subquestion list
                    question.subquestionList = [];
                    Subquestion
                        .subquestionsByQuestion({id:question[j].id})
                        .$promise
                        .then(function(subquestion){
                             //Add subquestion to the list
                             question.subquestionList.push(subquestion);
                        })
                   ;                        
                };
              })
            ;
        }
    });
}

The iteration of subquestions (ng-repeat) should be done based on the question iterator.

<div ng-repeat="question in vm.questionList">
   {{question.name}}
   <div ng-repeat="subquestion in question.subquestionList">
     {{subquestion.name}}
   </div>
</div>

It's important to note that a subquestionList property has been included in each question within the questionList.

Updating scope within an iteration in AngularJS

Answer №1

Answer №2

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