Unable to access Angular $scope outside of the specified function

Just started diving into Angular and javascript. I've constructed a controller that uses a factory service to retrieve data from a local JSON file. The majority of my code is inspired by, or directly copied from this article by Dan Wahlin. I'm having trouble accessing the $scope.books variable outside of the function and can't seem to pinpoint the issue. When I use console.log inside the function, I see the desired object, but it returns undefined when used outside. Any suggestions on what might be going wrong here? Thank you.

app.controller('FormController', ['$scope', 'tocFactory', function ($scope, tocFactory) {

  $scope.books;

  getBooks();

      function getBooks() {
        tocFactory.getBooks().
          success(function(data, status, headers, config) {
            $scope.books = data;
            console.log($scope.books);
          }).
          error(function(data, status, headers, config) {
            // log error
     })
  }
  console.log($scope.books);
  }]);

Answer №1

When working with ajax, it's important to remember that executing the next line of code does not guarantee that your ajax response is ready.

To ensure you have access to the response value, make use of the success function in the $http method, which is called when the ajax call is successful.

Interested in how asynchronous calls work? Check out this link: How asynchronous call works?

Answer №2

It's not a matter of scope, but rather timing. The getBooks function runs asynchronously, so when you log to the console, it may not have been bound to anything yet. You can easily test this by using an interval to observe how this unfolds:

app.controller('FormController', ['$scope', 'tocFactory', function($scope, tocFactory) {
  $scope.books;
  getBooks();
  function getBooks() {
    tocFactory.getBooks()
      .success(function(data, status, headers, config) {
        $scope.books = data;
        console.log($scope.books);
      })
      .error(function(data, status, headers, config) {
        // log error
      })
  }
  setInterval(function(){
    console.log($scope.books);
  }, 1000);
}]);

Answer №3

If you want to handle asynchronous code using promises, you can utilize the $q service in your AngularJS application:

app.controller('FormController', ['$scope', '$q', 'tocFactory', function ($scope,  $q, tocFactory)
{

    var getBooks = function()
    {
        var deferred = $q.defer();

        tocFactory.getBooks().
        success( function(data, status, headers, config)
        {
            $scope.books = data;
            deferred.resolve();
        } ).
        error( function(data, status, headers, config)
        {
            deferred.reject();
        } );

        return deferred.promise;
    };

    getBooks().then( function(res)
    {
        console.log($scope.books); // success : your data
    }, function(res)
    {
        console.log($scope.books); // error : undefined
    } );

    console.log($scope.books); // undefined

} ] );

Please note that I have not tested this specific code, but it should demonstrate how promises work with the $q service. For more information on the $q service, you can refer to: https://docs.angularjs.org/api/ng/service/$q

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