Monday, 16 February 2015

An Insight Into Two-Way Binding In AngularJS

Indubitably, single-page applications offer great accessibility and for this reason, it's highly admired by app developers. However, developing a single page application is not a child's play.

Since, mobile apps are ruling the ground currently, there is a great demand of android or iPhone app development services in the market. Fortunately, there are several web app frameworks available in the market that makes app development a breeze, but the amazing features of AngularJS make it stand ahead of its competitors.

There are numerous utile features offered by the open source framework – AngularJS (aka Angular), and two-way binding is the ultimate benefit of using this framework. This article will reveal the principle behind this feature and how to implement it in an AngularJS environment. For this, it is assumed that you possess a basic understanding of JavaScript.

How the Angular model is different from the traditional MVC model

Traditional MVC frameworks: Here models establish a connection between an application and the back-end database. Whenever an app is implemented, the corresponding MVC model is accessed and the data is retrieved; then the retrieved data are further merged with the view template, and this way a user version is created. Now, the controller keeps generating query to the model while, a user clicks on the interface of the user version. By reloading the page, the retrieved data become visible to the view (due to AJAX, small data sets don't demand page reloading).

For this, a developer needs to endeavor for proving this capability and certain explicit view changes are also required. If you look for an Android or Hire iPhone App Developer, to accomplish your project with utmost ease and precision. And once, you will learn this framework, you will be able to easily maintain your project and tweak it for better functioning.

AngularJS model: In an AngularJS app, the model and the view are interlaced. The data sourcing is managed by the model via the view. It is then turned around and passed back into the view. That is, no additional developer's effort is needed, only a few simple configurations and it is done.

Code Snippet:

<body data-ng-app=”sampleApp”>
<div data-ng-controller="SampleController as sample"
<input type="text" data-ng-model="yourName" />
<h2>{{ yourName }}</h2>
var sampleApp = angular.module(‘sampleApp’,[]);
sampleApp.controller( SampleController, function ( $scope ) {

Here, it can be observed that in the most trivial situation, the view and the model can instantly accomplish a bidirectional data sharing. Therefore, there is no need to implement a user-defined controller. Due to this close relationship, the models simply manipulate the data in the view and move around.

Binding: Ultimate features of AngularJS framework

The AngularJS also helps efficiently implement regular HTML for creating view templates. As soon as the AngularJS continues the DOM processing, all the elements that are not embracing any AngularJS hooks are certainly ignored. This facilitates Angular to deliver an efficient solution, whether it is connected to a root element or not. Now, whenever the HTML template comes into a view, all the elements featuring hooks eventually become “bounded”.

In the binding process, a property “$scope” is attached to the hooks. Therefore, every time when there is a variation in a “$scope” property, the bound element also changes accordingly (as represented in the aforementioned code snippet).

$scope: It is a property, not the controller. It is a plain old JavaScript object and the bound view elements turn into their respective $scope property. And, the idea of a direction is a way to better understand the relationship between bound elements of the associated $scope property.

A bound $scope property can be rendered into the view by implementing the below mentioned lines of code.

Code Snippet:

<span ng-bind=”firstName”></span>

Thus, binding can be explained as a relationship that doesn't exhibit any direction. Here, it is the relationship between bound elements that are related to the “$scope” property.

Two-way Binding

To elaborate the two-way binding, let's consider the following chunk of code from the first code snippet.
sampleApp.controller( SampleController, function ( $scope ) {
$scope.yourName = “Miley”;
<input type="text" data-ng-model="yourName" />
<h2>{{ yourName }}</h2>

With this code fragment, according to the two-way binding,
  • When the HTML template renders into a view, the “$scope” property replaces the “yourName”.
  • Now, when a new name is entered by a user in the text field, a listener becomes active. After this, the AngularJS immediately updates the “ $scope“ property with the user-typed text.
Eventually, then the bound view elements with that $scope property are also updated.

Final Thought

Whether it is one-way binding or two-way binding, the compiling process of Angular influences the binding process. With compilation, the genuine HTML and all the child nodes (that are existing within the ngApp directive) are evaluated. The AngularJS after identifying the pure HTML (which is also known as a template), enables all the associated models and directives to the $scope property. Thereby, resulting a template into the live view.

You can update the live views in a desired fashion by implementing the private event loop of AngularJS, that is, $digest(). This loop facilitates Angular to take care of all the real time events. Whenever a change in model's value is suspected, this loop is executed to determine whether there is any change or not by comparing the values.

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