Wednesday, 10 December 2014

Some Guidelines to Design Clean Controller and Service

An AngularJS controller should not be burdened with other tasks other than mediating interaction between view and data that comes from one or more services. The data model, data management and application business logic should be written in services. I also like to use controllerAs with 'this' approach. Also include as few services as possible in the controller. If a controller has too many services then this should be questioned. Instead we should try to use services that aggregate other required services inside.

Below is an example of a controller:
myApp.controller('MedicineCtrl', ['medicineService',
 function (medicineService) {
     var vm = this;
     vm.medicineNames = medicineService.medicineNames;
     vm.addMedicine = function (input) {
         medicineService.addMedicine(input);
     };
     vm.updateMedicine = function (input) {
         medicineService.updateMedicine(input);
     };
     vm.deleteMedicine = function (id) {
         medicineService.deleteMedicine(id);
     };
}]);
Of course, this is a simplified example however this should give us a picture of what a controller should be designed like.

For the service, it's recommended to have 'private' variables and functions needed and only expose publicly the ones that are necessary as service object's properties. Also whenever possible, try to design the functions to run asynchronously using AngularJS promise (will show an example in the next post). Below is an example of a service:
myApp.factory('medicineService', ['otherService1', 'otherService2', 
  function (otherService1, otherService2) {
    // 'private' variables and functions
    var _medicines = [];
    var _privateVarOne;
    var _privateVarTwo;
    
    _addMedicine = function (input) {
       . . .
       // some business logic
       . . .
    };

    _updateMedicine = function (input) {
       . . .
       // some business logic
       . . .
    };

    _deleteMedicine = function (id) {
       . . .
       // some business logic
       . . .
    };

    _anotherPrivateFunction = function () {
       . . .
       // some business logic
       . . .
    };

    // only expose publicly the required members
    return {
        medicineNames: _medicineNames,
        addMedicine: _addMedicine,
        updateMedicine: _updateMedicine,
        deleteMedicine : _deleteMedicine 
    }
}]);

Wednesday, 3 December 2014

AngularJS ControllerAs and Scope

If we set up a view and controller with controllerAs like below:
// in routing configuration
. . .
.when('/pageOne', {
        templateUrl: 'partials/page-one.html',
        controller: 'CtrlOne',
        controllerAs: 'vm'
})
. . .
// the controller
userApp.controller('CtrlOne', [function () {
    var vm = this;
    vm.nameOne = "test";
    vm.getName = function () {
        return 'aaa';
    };

    this.nameTwo = "blah";
    var nameThree = "ggg"; // not visible from outside
}]);
then we will have these scopes when the page loads:



The first scope is the root scope and the one underneath it is the scope created for the controller. As the picture shows, the variables are created as properties of 'vm' object. If we had used the traditional approach by defining variables on $scope such as $scope.myVariable = ... then these variables would be created on the first level on controller scope (not wrapped inside an object). We can also see when we use controllerAs, other variable that is defined directly not through 'this' object will not be visible from outside.


Adding a Child Controller

Let us add a child controller inside our controller. The child controller:
userApp.controller('ChildCtrl', [function () {
    var vm = this;
    vm.dataOne = 'sss';
    vm.getData = function () {
        return 'bbb';
    }
}]);
And change our view to be like this:
<div>
    Page One
    <div>
        <div>{{parentVm.nameOne}}</div>
        <div ng-controller="ChildCtrl as childVm">
            {{childVm.dataOne}}
            {{parentVm.nameOne}}
        </div>
    </div>
</div>

Now we can see that a new scope is created for the child controller:




Accessing Parent Controller's Variables

On the view, we can simply use '{{parentVm.variableName}}' to refer to a parent controller's variable.

In the child controller script function, accessing parent's variables which controller uses controllerAs is not as easy as if the parent controller had used $scope to register its properties. One way to do this is by using $scope help in the child controller. We need to inject $scope to the controller then refer to the parent controller's instance name to be able to access its variables/properties. Below is an example:
$scope.parentVm.nameOne = 'modify parent var';
//$scope.$parent.parentVm.nameOne = 'modify parent var';    // or could use $parent
The code on the first line is utilising JavaScript prototypal inheritance where it will try to find the property 'parentVm.nameOne' on the current scope then if it is not found, it will try to find on the parent scope and so on until it reaches the root scope. This AngularJS documentation 'Understanding Scope' explains it in more details.
The second code is finding the property on the parent scope. We could append many $parent if required.

If we had tried to do these below inside child controller:
vm.nameOne = 'modified';
$scope.nameOne = 'hhh';
new variables would be created on the current scope. One is on the scope's root level and the other one is inside an object. The picture below shows this:




Creating Local Variables that Hold References

If we want to create a local variable that holds reference to a variable in parent controller then we need to create that variable as an object in parent controller. This is explained as well in the referred AngularJS documentation above. For example:
// create an object variable in parent controller
vm.objVar = { name: 'aaa' };
then in our child controller:
// create the local variable in child controller
vm.childRefVar = $scope.$parent.parentVm.objVar;

// try to do some update
$scope.$parent.parentVm.objVar.name = 'jjj'; // when we update the variable in parent controller, this will reflect in both parent and local variables
vm.childRefVar.name = 'bbb'; // when we modify the local variable, this will reflect in parent variable as well


Best Practices

As we have seen above, accessing variables in parent controller is not straight forward. If you are going to have nested controllers in your view, it is recommended to use a service to share data between the controllers rather than using variables/properties in your controller.

If you do not want to use a service then I think it is better to register the variables or functions that are going to be shared on $scope rather than on 'this' object unless you are going to decide/know the controller's alias object name in advance to be used from codes inside child controller.

Thursday, 13 November 2014

Cordova Plugin is not Available when Application Starts

If you use a plugin and execute its method when your application starts and have this error:
TypeError: Cannot read property '[your_plugin_name]' of undefined at Object.[plugin_method]
then it is likely that the plugin has not been initialised fully when the method is called.

To solve this issue, wait until deviceready event is fired before calling the plugin's method.

With AngularJS, I like to wait until deviceready event is fired before loading the whole application. To do this, make sure that ng-app declaration is removed from the HTML, then bootstrap the app when deviceready event has fired. document.addEventListener is used to determine whether the event has been fired.
document.addEventListener("deviceready", function() {
    angular.bootstrap(document, ["myApp"]);
}, false);
If you want to apply this to a particular element instead of the whole HTML document (or body), you could use:
var theElement = document.findByID(...) // or document.querySelector(...);
angular.bootstrap(theElement, ["myApp"]);

Then you can call the rest scripts:
var myApp= angular.module('myApp', [. . .]);

myApp.config(
  . . .
);

Thursday, 23 October 2014

Adding ngCordova Plugin to Visual Studio Cordova Project

We will see how to add a plugin from ngCordova which has a collection of Cordova API plugins wrapped in AngularJS. ngCordova will help even more Cordova developers who are using AngularJS.

1. First, include ng-cordova.js or ng-cordova.min.js file into our project structure. We can use bower to install that or download the zip file from its GitHub repository then find the js file inside.

2. On our project main page, add a reference to it before the reference to cordova.js file.
<script src="some_path/ng-cordova.min.js"></script>
<script src="cordova.js"></script>

3. Include 'ngCordova' in our app module. For example:
var myApp = angular.module('myApp', ['ngCordova', . . .]);

4. Add the intended plugin wrapped by <vs:feature></vs:feature> inside <vs:features> node in our project config.xml file like below:
<vs:features>
  <vs:feature>plugin_id@version_number</vs:feature>
  <vs:feature>plugin_2_id@version_number</vs:feature>
  . . .
</vs:features>
Right click config.xml file then select View Code to do this.

To find the plugin Id and version number, we can check from plugins.cordova.io site or from the plugin.xml file on the plugin repository site. However if we are getting the information from plugin.xml file, that will always be the latest version which sometimes is not the stable one.

An example for the latter one, say we would like to use Local Notification plugin. Go to its site https://github.com/katzer/cordova-plugin-local-notifications then open plugin.xml file located on the root. Inside the plugin element there are 'id' and 'version' attributes.

When building the project, Visual Studio will download the plugin and add to the project if it has not done so.


5. Inject the plugin service into our controller then we can start using it.
For example, to use Local Notification, we need to inject $cordovaLocalNotification like this:
myApp.controller('MyCtrl', ['$cordovaLocalNotification', . . . ,
  function ($cordovaLocalNotification, . . .) {
  . . .
}]);

Friday, 10 October 2014

Basic Navigation in Ionic

On this post we will see how to do basic navigation in Ionic Framework.

1. First we need to configure the routes in AngularJS:
app.config(function($stateProvider, $urlRouterProvider) {
  $stateProvider
  .state('home', {
    url: '/',
    templateUrl: 'home.html'
  })
  .state('pageOne', {
    url: '/page1',
    templateUrl: 'one.html'
  })
  .state('anotherPage', {
    url: '/whatever',
    templateUrl: 'myhtml.html'
  });
  
   $urlRouterProvider.otherwise("/");
});
In the example we use UI Router to manage our routes. Each route has a state name, a defined url and an actual path for the view content. In the end, we also define the default url to be called when a url targeted does not match any in configurations.


2. Then on our main page, we just need to use
<ion-nav-view></ion-nav-view>
It will be useful to add a navigation bar with back button and also to have an animation effect like this:
<ion-nav-bar class="bar-positive">
        <ion-nav-back-button class="button-icon ion-arrow-left-c">
        </ion-nav-back-button>
    </ion-nav-bar>

    <ion-nav-view animation="slide-left-right"></ion-nav-view>
When we use Ionic navigation back button, the scripts behind it automatically do the job in storing page histories and pulling out the previous page as well as redirecting to the page when clicking the element.


3. Finally create each partial view using
<ion-view>
  <ion-content>
    . . .
  </ion-content>
</ion-view>


For a complete working example, please see here in Plunker.

Friday, 3 October 2014

Navigation in MVVM Light using Messenger

There are a few ways to implement navigation in MVVM Light based application. One of them is to use the Messaging framework of the toolkit. We will see a simple example of how to do this on Windows Phone.

1. First, in our view, we need to register to listen for a message that we want to receive :
Messenger.Default.Register<uri>(
this,
"MyToken",
(uri) => NavigationService.Navigate(uri)
);
We can put this in the view constructor or OnNavigatedTo() method. This code is saying that I want to register to receive any message that delivers uri type that uses 'MyToken' token. If there is any then I will execute an action which in this case is calling NavigationService.Navigate(uri).


2. Then in the view model, we need to create a command to trigger the message that will be broadcasted.
We add a RelayCommand property for a navigation command:
public RelayCommand NavigateCommand { get; private set; }
Then in the view model constructor we initialise that (or could be on the property getter above):
NavigateCommand = new RelayCommand(() =>
{
Messenger.Default.Send<uri>(new Uri("/PageName.xaml", UriKind.Relative), "MyToken");
});


3. Finally bind the command property to a control on the view xaml file using:
Command="{Binding NavigateCommand}"


Soon we will have many repetitive codes in our views, so we could put the codes to register for the message in a base class like this:
public class BasePage : PhoneApplicationPage
{
 protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
 {
 Messenger.Default.Register<uri>(this, "MyToken", uri => NavigationService.Navigate(uri));
 base.OnNavigatedTo(e);
 }

 protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
 {
 Messenger.Default.Unregister<uri>(this);
 base.OnNavigatedFrom(e);
 }
}
So we just need to make our views inherit from this class.

On our xaml files, we also need to replace
<phone:PhoneApplicationPage
to
<phone:BasePage

and also
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
to
xmlns:phone="clr-namespace:YourNamespace"


Another way to do navigation is by creating our custom navigation service to be used in our view models. This nice article, explains how to implement it in details.

Thursday, 2 October 2014

Getting Started with Cordova and Ionic in Visual Studio

On this post, we will see how to install Visual Studio Apache Cordova tool and Ionic framework and get started with a sample application.

1. First we need to download and install Apache Cordova tool from here. At the time of writing, the version is CTP 2.0.

2. Then once completed, open Visual Studio to create a new project. On the New Project dialog, go to JavaScript project templates then Multi-Device Hybrid App. Select Blank App (Apache Cordova) then create a project.

3. Install Ionic through NuGet. At the time of writing, the latest version is v1.0.0.0-beta.1. This will add many AngularJS and Ionic files into our project.

4. Install Ionic on local machine so that we could create some sample applications with particular templates and use some of the files in our project. To do this, open Node.js command prompt then run this command:
npm install ionic -g
-g is used to install the package globally

5. On the command prompt, go to a directory where you want to have Ionic sample applications then run this command:
ionic start SideMenuAppExample sidemenu
This command will generate a sample Ionic application with side menu navigation.

6. Go to the generated app folder then to 'www\js' folder then copy app.js and controllers.js into our project.

7. Also copy the whole 'templates' folder and its content into our project.

8. Then on our project index.html file:
- add a reference to 'Content/ionic.css'
- add a reference to 'scripts/ionic.bundle.js'
- add references to the two JavaScript files that we have copied over (app.js and controllers.js)
- add 'ng-app="starter"' in the body
- add <ion-nav-view></ion-nav-view> inside the body content

Once finished, we will have something like this on our index.html:
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>BlankCordovaApp2</title>

    <link href="Content/ionic.css" rel="stylesheet" />
    <link href="css/index.css" rel="stylesheet" />
</head>
<body ng-app="starter">
    <ion-nav-view></ion-nav-view>


    <!--library scripts references-->
    <script src="scripts/ionic.bundle.js"></script>
    <script src="cordova.js"></script>
    <script src="scripts/platformOverrides.js"></script>
    
    <!--custom scripts references-->
    <script src="app.js"></script>
    <script src="controllers.js"></script>
</body>
</html>

Then run the application. We should see a sample app with side menu running.