Angular 5 -Complete guide to build SPA(Part 4)

Routing

Routing in angular is one of the core feature which enable navigation between views based on user input. Router module is defined in @angular/router.

How it works

In single page application, there will be a master view which gets loaded when the app is rendered in browser initially. The child view gets loaded into the master view asynchronously based on the matching url structure.

The same logic applies on the child view as well in case of nested routes. 

The above image explains how routing works from higher master page level to component at lower level.

index.html is by default the initial page which gets loaded when the application gets loaded in the browser. This view contains a <app-root>  tag, which is not a normal html tag but it tells the angular router to load the bootstrapped AppComponent.

<app-root></app-root> get loaded with the app.component.html which is the bootstrapped component in our case.

app.component.html contains <router-outlet></router-outlet> which helps to load the views/components based on the routing url.

Step 1: Navigation Menu

As the initial step, i'm going to design menu navigation menu. It can be done either in app.component.html or create a new header component for better seperation.

Adding a new header component in component folder using below command.

d:\Jithin\Angular.Sample\src\app\component>ng g component header 

header.component.html

header component html looks like below.

<nav class="navbar navbar-inverse">

<div class="container-fluid">

<div class="navbar-header">

<button type="button" class="navbar-toggle" data-toggle="collapse"
data-target= "#appNavigationBar">

<span class="icon-bar"></span>

<span class="icon-bar"></span>

<span class="icon-bar"></span>

</button>

<a class="navbar-brand" href="#">Angular.Sample</a>

</div>

<div class="collapse navbar-collapse" id="appNavigationBar">

<ul class="nav navbar-nav">

<li>

<a [routerLink]="['/EmployeeDashboard']" routerLinkActive="active">Dashboard</a>

</li>

<li class="dropdown">

<a class="dropdown-toggle" data-toggle="dropdown" routerLinkActive="active">Employee

<span class="caret"></span>

</a>

<ul class="dropdown-menu">

<li>

<a [routerLink]="['Employee/AddEmployee']" routerLinkActive="active">Add Employee</a>

</li>

<li>

<a [routerLink]="['Employee/EditEmployee']" routerLinkActive="active">Edit Employee</a>

</li>

</ul>

</li>

</ul>

<ul class="nav navbar-nav navbar-right">

<li>

<a href="#">

<span class="glyphicon glyphicon-user"></span> Sign Up</a>

</li>

<li>

<a href="#">

<span class="glyphicon glyphicon-log-in"></span> Login</a>

</li>

</ul>

</div>

</div>

</nav>

app.component.html

<!--header component-->

<app-header></app-header>

Step 2: Add child component

Each and every route would need a component to  be created. I'm going to create the child components based on my example.

This is how the component folder looks after adding the necessary components.

Step 3: Configuring the routes

This step is one of the important step in routing. Route configuration is done in app.module.ts .

Import the angular router module as below.

import { RouterModule, Routes } from '@angular/router';

Define the the required routes with its path and component.

const employeeChildRoutes =[

{ path: '', redirectTo: 'AddEmployee', pathMatch: 'full' },

{ path: 'AddEmployee', component: AddEmployeeComponent },

{ path: 'EditEmployee', component: EditEmployeeComponent },

];

const appRoutes: Routes = [

{ path: '', component: EmployeeDashboardComponent },

{ path: 'EmployeeDashboard', component: EmployeeDashboardComponent },

{ path: 'Employee', component: EmployeeComponent, children:employeeChildRoutes },

];

A route array can take different parameters.Below are the main 4 parameter which will come handy in any  normal application.

1. path which defines the url structure 
2. component associated with the path
3. children , this helps in configuring the nested route and its again the type of route array. In the above example, you can see employeeChildRoute which is of type route array is assigned as children of Employee path.
4. canActivate  is useful  when you want to perform some pre-processing logic before activating the route. Eg: if you want to restrict the page access for logged in user alone, this check can be done using canActivate with the help of an authgaurd.

Add the routes into the imports array. Modify the import array like below.

imports: [

BrowserModule,

RouterModule.forRoot(appRoutes, {useHash: true})

],

There are different location strategy available in angular. In this example , I'm using HashLocationStrategy. {useHash: true}

4. <router-outlet> tag in parent components

Place <router-outlet></router-outlet> tag in all your  parent component which loads the child component based on the route.

In above example, i have placed the above tag in AppComponent and EmployeeComponent which are my parent components according to the defined route.

<!--header component-->

<app-header></app-header>

<router-outlet></router-outlet>

Output 

The final output of above code looks like below.

Angular 5 - Complete guide to build SPA (Part 2)

Angular Architecture

One of the major design considerations in angular is to reduce the size of the final bundle, with this, some of the libraries that are required for angular app to work are provided through core libraries, and other optional libraries can be  imported as per needs.

Components are the basic building blocks of angular applications, this uses other dependencies like services, directives etc to perform its task.

Below architecture diagram can give a better idea on how each parts interact each other.

Modules

Angular Modules contains different parts of the application and are the way to group related component, services, directives and pipes to a single unit.

Component

Major development in angular is done using component. Each component is linked to view. It can be viewed as a reusable component as well.

Components are part of ngModules and each component can use other components as well. It can be viewed as a tree structure.

Template represents the html view and it communicates with the component through property and events.

Services are nothing but reusable functions that are separated from components but can be injected through dependency injection. This is very useful when you want to use same methods or properties in multiple places.

Routing

When it come to Single Page Application(SPA), we often hear angular associated with it. Angular is designed to mainly with the objective of SPA. Angular router framework evolved over the years and become a well matured framework to support all needs of SPA.

Routing works based on the URL structure. It allows us to define the routes and its corresponding components using a Route array.  When the URL matches the defined route, its component get loaded in to main template.

Angular 5 - Complete guide to build SPA (Part 1)

Angular 5 - Introduction

The purpose of this blog is to provide complete details about building an angular app using typescript and Angular CLI. 

Angular CLI is the new command line interface introduced with angular which helps the developer in the development process. It helps to create, build, run and test the required components through CLI commands.  

Why Angular 5?

Many developers who are familiar with previous version of angular like Angular JS, Angular 2/4 would certainly have doubts in their mind about this. Why angular 5?

To answer this, we need to compare each of these and what new changes have been introduced with  new version. There is a major difference in features with angular js and angular versions but angular 2,4 and 5 are almost same with some improvement iterations in the higher versions.

Angular JS vs Angular

Angular is a major update over angular js in terms of syntax as well as functionality.

1. JavaScript vs TypeScript   -  Angular is written using TypeScript which is the superset of  JavaScript. It takes the advantage that typescript is the only typed language that compiles into javascript. TypeScript makes code easier to read and understand.
2. Component based Architecture   - Angular application architecture helps to create components that don't depend on each other, which are loosely coupled as possible.
3. Mobile Oriented Architecture- Angular was designed keeping in mind about the present needs. It designed a framework that can support both mobile app development as wells as web apps. NativeScript helped in angular mobile development faster and effective.
4. View Engine -  The new view engine introduced helps in generating a smaller code using Ahead of Time (AOT) manner. 
5. Animation Package - Animation package was removed from the core package in angular. This was because most of the applications doesn't use animations, so this can be removed from core package which will help to reduce the size of the build. This was also done thinking about mobile application development.
6. Perfomance  - Angular applications are smaller and faster. It consumes less space and run faster which helps in increasing the overall performance of the application.

These differences listed above are with respect to angular js. There are not much difference in Angular 2 , 4 or 5. Its just the performance improvements or the minor functionality improvements. 

Why Angular 4 Not 3?

This would be a question in all developers mind why not 3 after angular 2.

Answer  is simple and it was nothing related to any functionalities introduced, but with the versioning of packages. 

Please refer below image:

When angular 2 was released, the version of angular/router package was already 3. This created some confusion in the developer mind regarding the versions. 

In order to make the versions of the packages same, version 3 was skipped and all the packages were versioned as 4 in the next major release. 

We will be discussing about angular architecture and development environment setup in next blog.