Encountering an unspecified outcome in an Angular DataFactory due to an HTTP POST Request

I just started learning Angular.js and I'm experimenting with using a factory to send data through an http post request. However, I encountered an error that says

Cannot read property 'success' of undefined
. Here is the code snippet in question...

<!DOCTYPE html>
<html ng-app="myApp">
<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>

<body>
    <div ng-controller="myCtrl">

    </div>

    <script>
        var app = angular.module('myApp', []);

        app.factory('DataFactory', ['$http', function($http) {
            return {
                setData: function(stud) {
                    return
                    $http({
                        method: 'POST',
                        url: 'http://www.w3schools.com/jquery/demo_test_post.asp',
                        headers: {
                            'Content-Type': 'application/x-www-form-urlencoded'
                        },
                        data: stud
                    });

                }
            }

        }]);

        app.controller('myCtrl', function($scope, DataFactory) {

            var stud = {
                name: "Alex",
                city: "Berlin"
            };


            DataFactory.setData(stud).then(function(response) {
                    console.log(response);
                })
                .catch(function(err) {
                    console.error(err)
                })
                .finally(function() {
                    console.log("Finished the chain");
                });
        });
    </script>

</body>

</html>

The specific error appears at line where it says DataFactory.setData(stud).success... any assistance would be greatly appreciated...

Answer №1

According to the documentation:

var promise = someAsyncMethodCall();
promise.then(function(greeting) {
  alert('Success: ' + greeting);
}, function(reason) {
  alert('Failed: ' + reason);
});

In the above code snippet, you can see that there are two functions being passed to the then function. Your code should look something like this:

DataFactory.setData(stud).then(function(response) {
     console.log(response);
}, function (err) {
     console.error(err)
});

The $q library is utilized by $http internally.

Refer to the promise API documentation.

The following methods are available:

then(successCallback, errorCallback, notifyCallback) – This method calls either the success or error callback asynchronously as soon as the result is available, regardless of when the promise was resolved or rejected. The callbacks receive a single argument: the result or rejection reason. Additionally, the notify callback may be invoked zero or more times to indicate progress before resolution or rejection.

The return value of the successCallback, errorCallback resolves or rejects a new promise (unless it's a promise itself, in which case it's resolved with the value of that promise using chaining). The notifyCallback method indicates progress. Resolution or rejection cannot occur from the notifyCallback method.

catch(errorCallback) – A shortcut for promise.then(null, errorCallback)

finally(callback, notifyCallback) – Allows observation of whether a promise is fulfilled or rejected without altering the final value. Useful for releasing resources or performing clean-up tasks regardless of rejection or resolution. Refer to the full specification for more details.

To enhance your code further, consider the following:

DataFactory.setData(stud).then(function(response) {
    console.log(response);
})
.catch(function (err) {
    console.error(err)
})
.finally(function () {
    console.log("Chain execution completed");
});

--- EDIT ---

Another issue mentioned by @Duncan is regarding the line break:

app.factory('DataFactory', ['$http', function($http) {
    return {
        setData: function(stud) {
            return
            $http({
                method: 'POST',
                url: 'http://www.w3schools.com/jquery/demo_test_post.asp',
                headers: {
                    'Content-Type': 'application/x-www-form-urlencoded'
                },
                data: stud
            });

        }
    }

}]);

The line break between return and $http({ needs to be removed to resolve the error. It should be revised as follows:

app.factory('DataFactory', ['$http', function($http) {
    return {
        setData: function(stud) {
            return $http({
                method: 'POST',
                url: 'http://www.w3schools.com/jquery/demo_test_post.asp',
                headers: {
                    'Content-Type': 'application/x-www-form-urlencoded'
                },
                data: stud
            });

        }
    }

}]);

Answer №2

When using the $http function, it will return a Promise. Remember to utilize the .then() method to set up a callback for when the request is successful.

An alternative way of writing this is by using the following format: .then(successFn, failFn)

Answer №3

The issue lies within the function setData():

                return
                $http({
                    method: 'POST',
                    url: 'http://www.samplewebsite.com/test-post',
                    headers: {
                        'Content-Type': 'application/json'
                    },
                    data: studentData
            });

You have two statements here: the first return simply exits the function, and the subsequent call to $http() is never executed.

Make sure to be mindful of where you place line breaks in your Javascript code, move $http({ up to the previous line.

In addition, it's worth noting that using .success with $http results is now considered outdated; opt for traditional promise methods instead.

Answer №4

Is there a specific markdown rule, or is it crucial to have a line break between return and $http? Failing to add a line break will make $http unreachable. It is okay to place functions below the return statement since they are registered before the code is executed.

Therefore, the proper way to write it is

return $http({...})

rather than

return $http({...})

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