Return error to Angular from Express

Question

I have a application where users can add movies to their watchlist. I want to prevent users from adding a movie that already exists in their watchlist.

This my addMovie function in my Angular controller:

$scope.addMovie = function (movie)  {
    movieFactory.selectMovie(movie).then(function(response){
        movieFactory.addMovie(response);
        Notification.success(movie.title + ' has been added to your watchlist');
        $scope.movies = [];
        $scope.overlay = false;
        $scope.searchquery = '';
        $rootScope.$broadcast('onAddMovieEvent', response);
    });
};

I pass the movie object through from my initial ng-click. Then I request a selectMvoie function in the movieFactory that gets the correct movie data from the TMDB api.

Then I call the addMovie function in the movieFactory factory with the response from selectMovie function.

factory.addMovie = function (movie) {
    var deferred = $q.defer();
    $http({
        method: 'POST',
        url: '/movies',
        data: movie
    })
        .success(function (data) {
            deferred.resolve(data);
        })
        .catch(function () {
            deferred.reject();
        });
    return deferred.promise;
};

This does a /post request which goes into my Express route:

router.post('/', function(req,res){
    pool.getConnection(function(err, connection) {

        connection.query('SELECT * FROM user_movieid WHERE movie_id= ? AND userid= ?' ,[req.body.id, req.user.id] , function(err, result) {
            for (var i = result.length - 1; i >= 0; i--) {

                if (movie.id === result[i].movie_id) {
                    console.log('exists');
                }
            }
        });
    });
})

There's also a connection.query that posts the movie into the database but that's not relevant now.

My situation now is that when I post a movie that already exists my node console shows the message exists but still posts the movie (obviously).

How would I return an "error" status back to my addMovie function in my Angular controller so I can do a if statement to show a different notification?

Ryan · Accepted Answer · 2016-08-25 17:31:06Z

If you want to keep your API 'restful' then I would return a response with a non 2xx status code. I would think 409 Conflict is appropriate for this case.

router.post('/', function(req,res){
    pool.getConnection(function(err, connection) {

        connection.query('SELECT * FROM user_movieid WHERE movie_id= ? AND userid= ?' ,[req.body.id, req.user.id] , function(err, result) {
            for (var i = result.length - 1; i >= 0; i--) {

                if (movie.id === result[i].movie_id) {
                    console.log('exists');
                    // choose an appropriate status code, probably a conflict 409 in this case
                    return res.status(409).send('Movie already exists in your watchlist')
                }
            }
        });
    });
})

Then in your Angular code you can notify the user that the movie is already in their list.

$scope.addMovie = function (movie)  {
    movieFactory.selectMovie(movie).then(function(response){
        movieFactory.addMovie(response);
        Notification.success(movie.title + ' has been added to your watchlist');
        $scope.movies = [];
        $scope.overlay = false;
        $scope.searchquery = '';
        $rootScope.$broadcast('onAddMovieEvent', response);
    })
    // catch any errors
    .catch(function() {
      // ideally you should check the status code here and probably handle other non 409 status codes differently
      // since this .catch will execute for any other 4xx and 5xx errors
      Notification.fail(movie.title + ' is already in your watchlist');
    });
};

Thanks, I had to change the code a bit to get the .catch in the correct factory request but it's working now.

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