How to add dynamic fields with angularjs

I am working on a QA app where i need to add multiple answers to a question as per requirement dynamically. for this in my form I have a question field , an answer field and a Boolean correct field to tell if the answer choice is correct or not. I have given a button add another answer which create a new answer field when clicked.I want to give ng-model name dynamically so that I can easily retrieve the value of ng-model.
For this I have created a controller which is like

app.controller('questionsCtrl', function ($scope) {
    $scope.question={};
    $scope.question.answers=[];
    $scope.answer_choices=[];
    var choice=1;

    $scope.addAnswerField=function(){
        $scope.answer_choices.push(choice);
         choice++;
    }

    $scope.addAnswerChoice=function(){
        $scope.question.answers.push({});
    }

});

My HTML code is:

<div class="container">
    <form ng-submit="createQuestion()">
    <textarea class="form-control" ng-model='question.question_text'></textarea>
    <textarea  class="form-control" ng-model="question.answer_choice_1"></textarea>
    <label class="checkbox-inline">
    <input type="radio" name="correct" ng-model="question.correct_1" /> 
        Correct
    </label>
    <div ng-repeat="choice in answer_choices">
    <textarea  class="form-control" ng-model="question.answers.$index[answer]">

    </textarea>
    <label class="checkbox-inline">
        <input type="radio" name="correct" ng-model = "question.answers.$index[correct]" /> 
    </label>
    </div>
    <button  class='btn btn-primary' type="submit">Submit</button>
</form>
<button class="btn btn-default" ng-click="addAnswerChoice()">Add Answer</button>
</div>

I want to do something like when i add a new answer choice a new empty object is pushed in the question.answers array and this objects first key answer hold the value of question field and second key ` like

question.answers=[
                   {'answer':'',correct:''},
                   {'answer':'',correct:''},
                   {'answer':'',correct:''},
                   {'answer':'',correct:''},

]

Suggest me how can i do this . There is only one error that using $index i am unable to assign value to the array object at the same index in question.answers array. Or if there is any other better way suggest me. Help will be appreciated.