Is it possible for AngularJS to automatically update a view when a persistent model (stored in a server database) is altered by an external application?

Question

Is it possible for AngularJS to automatically update a view when a persistent model (stored in a server database) is altered by an external application?

I'm just beginning to explore AngularJS, however, I am interested in creating a web application that can automatically update the user interface in real-time without needing to refresh the page whenever there is a change in the server-side database.

Is it possible for AngularJS to handle this process mostly on its own? And if so, how does it work at a basic level?

For instance, do you have to configure AngularJS to regularly check the database for any changes in the "model"? Or do you need to implement a Comet-like mechanism to inform the AngularJS client-side code when the model has been updated?

In my scenario, the complication arises from other non-web server software updating the database occasionally. However, this question also pertains to pure web applications where multiple clients could be modifying the database through AngularJS web clients, and each client needs to be notified of any changes made by others.

javascript angularjs websocket socket.io

Answer 1

Answer №1

When faced with this scenario, there are several options available...

One approach is to implement polling at regular intervals using $timeout and $http. Alternatively, if the data is linked to a REST service, consider using $resource instead of $http.

Another solution involves creating a service that utilizes a Websocket implementation and leverages scope.$apply to manage updates pushed by the socket. Here is an example utilizing socket.io, a node.js websocket library:

// Angular factory for Socket
myApp.factory('Socket', function($rootScope) {
    var socket = io.connect('http://localhost:3000');

    //Override socket.on to $apply changes to angular
    return {
        on: function(eventName, fn) {
            socket.on(eventName, function(data) {
                $rootScope.$apply(function() {
                    fn(data);
                });
            });
        },
        emit: socket.emit
    };
})

function MyCtrl($scope, Socket) {
    Socket.on('content:changed', function(data) {
        $scope.data = data;
    });
    $scope.submitContent = function() {
        socket.emit('content:changed', $scope.data);
    };
}

An advanced option is to develop a websocket implementation that synchronizes an Angular model with the server. Any changes made by the client are automatically sent to the server, and vice versa for server-side modifications.
Check out this example from an older version of Angular, also incorporating socket.io: https://github.com/mhevery/angular-node-socketio

UPDATE: I have personally utilized Firebase for implementing the third option mentioned above.

Answer 2

When faced with this scenario, there are several options available...

One approach is to implement polling at regular intervals using $timeout and $http. Alternatively, if the data is linked to a REST service, consider using $resource instead of $http.

Another solution involves creating a service that utilizes a Websocket implementation and leverages scope.$apply to manage updates pushed by the socket. Here is an example utilizing socket.io, a node.js websocket library:

// Angular factory for Socket
myApp.factory('Socket', function($rootScope) {
    var socket = io.connect('http://localhost:3000');

    //Override socket.on to $apply changes to angular
    return {
        on: function(eventName, fn) {
            socket.on(eventName, function(data) {
                $rootScope.$apply(function() {
                    fn(data);
                });
            });
        },
        emit: socket.emit
    };
})

function MyCtrl($scope, Socket) {
    Socket.on('content:changed', function(data) {
        $scope.data = data;
    });
    $scope.submitContent = function() {
        socket.emit('content:changed', $scope.data);
    };
}

An advanced option is to develop a websocket implementation that synchronizes an Angular model with the server. Any changes made by the client are automatically sent to the server, and vice versa for server-side modifications.
Check out this example from an older version of Angular, also incorporating socket.io: https://github.com/mhevery/angular-node-socketio

UPDATE: I have personally utilized Firebase for implementing the third option mentioned above.

Answer 3

Answer №2

Check out this new approach using jetty instead of node for implementation. The angularjs segment is inspired by the angular-seed app. While I can't guarantee that the angular code is entirely idiomatic, it has been tested and proven to work effectively. Hope this helps! -Todd.

Explore TimerWebSocketServlet here

https://gist.github.com/3047812

controllers.js

// -------------------------------------------------------------
// TimerCtrl
// -------------------------------------------------------------
function TimerCtrl($scope, CurrentTime) {
    $scope.CurrentTime = CurrentTime;
    $scope.CurrentTime.setOnMessageCB(
        function (m) {
            console.log("message invoked in CurrentTimeCB: " + m);
            console.log(m);
            $scope.$apply(function(){
                $scope.currentTime = m.data;
            })
        });
}
TimerCtrl.$inject = ['$scope', 'CurrentTime'];

services.js

angular.module('TimerService', [], function ($provide) {
    $provide.factory('CurrentTime', function () {
        var onOpenCB, onCloseCB, onMessageCB;
        var location = "ws://localhost:8888/api/timer"
        var ws = new WebSocket(location);
        ws.onopen = function () {
            if(onOpenCB !== undefined)
            {
                onOpenCB();
            }
        };
        ws.onclose = function () {
            if(onCloseCB !== undefined)
            {
                onCloseCB();
            }
        };
        ws.onmessage = function (m) {
            console.log(m);
            onMessageCB(m);
        };

        return{
            setOnOpenCB: function(cb){
               onOpenCB = cb;
            },
            setOnCloseCB: function(cb){
                onCloseCB = cb;
            },
            setOnMessageCB: function(cb){
                onMessageCB = cb;
            }
        };
    })});

web.xml

<servlet>
    <servlet-name>TimerServlet</servlet-name>
    <servlet-class>TimerWebSocketServlet</servlet-class>
    <load-on-startup>0</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>TimerServlet</servlet-name>
    <url-pattern>/api/timer/*</url-pattern>
</servlet-mapping>

Answer 4

Check out this new approach using jetty instead of node for implementation. The angularjs segment is inspired by the angular-seed app. While I can't guarantee that the angular code is entirely idiomatic, it has been tested and proven to work effectively. Hope this helps! -Todd.

Explore TimerWebSocketServlet here

https://gist.github.com/3047812

controllers.js

// -------------------------------------------------------------
// TimerCtrl
// -------------------------------------------------------------
function TimerCtrl($scope, CurrentTime) {
    $scope.CurrentTime = CurrentTime;
    $scope.CurrentTime.setOnMessageCB(
        function (m) {
            console.log("message invoked in CurrentTimeCB: " + m);
            console.log(m);
            $scope.$apply(function(){
                $scope.currentTime = m.data;
            })
        });
}
TimerCtrl.$inject = ['$scope', 'CurrentTime'];

services.js

angular.module('TimerService', [], function ($provide) {
    $provide.factory('CurrentTime', function () {
        var onOpenCB, onCloseCB, onMessageCB;
        var location = "ws://localhost:8888/api/timer"
        var ws = new WebSocket(location);
        ws.onopen = function () {
            if(onOpenCB !== undefined)
            {
                onOpenCB();
            }
        };
        ws.onclose = function () {
            if(onCloseCB !== undefined)
            {
                onCloseCB();
            }
        };
        ws.onmessage = function (m) {
            console.log(m);
            onMessageCB(m);
        };

        return{
            setOnOpenCB: function(cb){
               onOpenCB = cb;
            },
            setOnCloseCB: function(cb){
                onCloseCB = cb;
            },
            setOnMessageCB: function(cb){
                onMessageCB = cb;
            }
        };
    })});

web.xml

<servlet>
    <servlet-name>TimerServlet</servlet-name>
    <servlet-class>TimerWebSocketServlet</servlet-class>
    <load-on-startup>0</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>TimerServlet</servlet-name>
    <url-pattern>/api/timer/*</url-pattern>
</servlet-mapping>

Answer 5

Answer №3

If you're in need of it, check out Firebase and also have a look at Deployd. For an easier integration, Firebase provides an adapter that simplifies the process:

Answer 6

If you're in need of it, check out Firebase and also have a look at Deployd. For an easier integration, Firebase provides an adapter that simplifies the process:

Answer 7

Answer №4

The "Discover Meteor" book suggests that Angular's watches/scopes share similarities with Meteor's computations in terms of reactivity. However, Angular is limited to client-side functionality and offers less detailed control compared to Meteor.

From my perspective, integrating Angular may be more suitable for enhancing reactivity in an existing application, while Meteor excels when used for creating the entire project. I have not had much hands-on experience with Angular yet, although I have developed a few small apps using Meteor.

Answer 8

The "Discover Meteor" book suggests that Angular's watches/scopes share similarities with Meteor's computations in terms of reactivity. However, Angular is limited to client-side functionality and offers less detailed control compared to Meteor.

From my perspective, integrating Angular may be more suitable for enhancing reactivity in an existing application, while Meteor excels when used for creating the entire project. I have not had much hands-on experience with Angular yet, although I have developed a few small apps using Meteor.

Answer 9

Answer №5

In my perspective, Andy Joslin has brought up a great solution in his response, which is the 3rd option of maintaining state bidirectionally through websockets or any other asynchronous library being used (such as the Chrome message API for Chrome Extensions and Apps). toddg also shared an example of how this can be accomplished. However, it's worth noting that in his example, he is implementing an anti-pattern in AngularJS: having the service call the controller. Ideally, the model should reside within the service and then be accessed from the controller.

The service's socket callbacks will alter the service model, and because it's referenced in the controller, it will reflect those changes in the view. It's important to be cautious when dealing with primitive data types or variables that can be reassigned, as they will require a watch on the controller to ensure everything works smoothly.

Answer 10

In my perspective, Andy Joslin has brought up a great solution in his response, which is the 3rd option of maintaining state bidirectionally through websockets or any other asynchronous library being used (such as the Chrome message API for Chrome Extensions and Apps). toddg also shared an example of how this can be accomplished. However, it's worth noting that in his example, he is implementing an anti-pattern in AngularJS: having the service call the controller. Ideally, the model should reside within the service and then be accessed from the controller.

The service's socket callbacks will alter the service model, and because it's referenced in the controller, it will reflect those changes in the view. It's important to be cautious when dealing with primitive data types or variables that can be reassigned, as they will require a watch on the controller to ensure everything works smoothly.

Is it possible for AngularJS to automatically update a view when a persistent model (stored in a server database) is altered by an external application?

Answer №1

Answer №2

Explore TimerWebSocketServlet here

controllers.js

services.js

web.xml

Answer №3

Answer №4

Answer №5

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