Angular 2.0 Architechture

Starting new series – Learning Angular 2.0 on My Github –

##### angular 2.0 building blocks
– Module
– Component
– Template
– Metadata
– Data Binding
– Service
– Directive
– Dependency Injection

##### 1. Module
– Angular apps are modular and so in general we assemble our application from many modules. A typical module is a cohesive block of code dedicated to a single purpose.
– A module exports something of value in that code, typically one thing such as a class.
– Some modules are libraries of other modules.
– Angular itself ships as a collection of library modules called “barrels”. Each Angular library is actually a public facade over several logically related private modules.
– The angular2/core library is the primary Angular library module from which we get most of what we need.
– There are other important Angular library modules too such as angular2/common, angular2/router, and angular2/http.
– e.g import {Component} from ‘angular2/core’;
– The key take aways are:
    – Angular apps are composed of modules.
    – Modules export things — classes, function, values — that other modules import.
    – We prefer to write our application as a collection of modules, each module exporting one thing.
    – The first module we write will most likely export a component.

##### 2. Component
– Perhaps the first module we meet is a module that exports a component class. The component is one of the basic Angular blocks, we write a lot of them
– Most applications have an AppComponent. By convention, we’ll find it in a file named app.component.ts
– Components are the collection of templates, styles, selector configurations etc.
– Angular creates, updates, and destroys components as the user moves through the application.
– Each components is a typescript class which again includes variable, functions, prop declaration etc.

##### 3. Template
– We define a Component’s view with its companion template. A template is a form of HTML that tells Angular how to render the Component.
– A template looks like regular HTML much of the time … and then it gets a bit strange.
– Template will have all diff type databinding and html DOM information.

##### 4. Metadata
– Metadata tells Angular how to process a class.
– e.g
  selector:    ‘hero-list’,
  templateUrl: ‘app/hero-list.component.html’,
  directives:  [HeroDetailComponent],
  providers:   [HeroService]
Here we see the @Component decorator which (no surprise) identifies the class immediately below it as a Component class.

selector – a css selector that tells Angular to create and insert an instance of this component where it finds a <hero-list> tag in parent HTML. If the template of the application shell (a Component) contained

templateUrl – the address of this component’s template

directives – an array of the Components or Directives that this template requires.

providers – an array of dependency injection providers for services that the component requires. This is one way to tell Angular that our component’s constructor requires a HeroService so it can get the list of heroes to display.

##### 5. Data Binding
– There are four forms of data binding syntax.
– Each form has a direction – to the DOM, from the DOM, or in both directions.
– We can group all bindings into three categories by the direction in which data flows. Each category has its distinctive syntax:
    – One Way (from component -> View)   – Binds Property, Attributes, Class, Style.
    [target] = “expression”
    bind-target = “expression”
    – One Way (from View -> Component) – Binds Events
    (target) = “Statement”
    – Two way binding
    [(target)] = “expression”
    bindon-target =”expression”
For More Details –

##### 6. Directive
– Our Angular templates are dynamic. When Angular renders them, it transforms the DOM according to the instructions given by a directive.
– A directive is a class with directive metadata. In TypeScript we’d apply the @Directive decorator to attach metadata to the class.
– While the component is technically a directive, it is so distinctive and central to Angular applications that we chose to separate the component from the directive in our architectural overview.
– There are two other kinds of directives as well that we call “structural” and “attribute” directives.
– Structural directives alter layout by adding, removing, and replacing elements in DOM.
    – e.g *ngFor , *ngIf etc.
– Attribute directives alter the appearance or behavior of an existing element. In templates they look like regular HTML attributes, hence the name.
    – e.g. [(ngModel)]

##### 7. Service
– “Service” is a broad category encompassing any value, function or feature that our application needs.
– Almost anything can be a service. A service is typically a class with a narrow, well-defined purpose. It should do something specific and do it well.
    – Examples include:
        – logging service
        – data service
        – message bus
        – tax calculator
        – application configuration
– Most common usage of services are to bind components with Databases or any similar part which delivers data to components and that way, components will be independent from Data Layer.

##### 8. DI (Dependency Injection)
– “Dependency Injection” is a way to supply a new instance of a class with the fully-formed dependencies it requires. Most dependencies are services. Angular uses dependency injection to provide new components with the services they need.
– dependency injection is wired into the framework and used everywhere.
– the Injector is the main mechanism.
    – an injector maintains a container of service instances that it created.
    – an injector can create a new service instance using a provider.
– a provider is a recipe for creating a service.
– we register providers with injectors.

##### 9. Other Stuff
– Animation: A forthcoming animation library makes it easy for developers to animate component behavior without deep knowledge of animation techniques or css.
– Bootstrapping: A method to configure and launch the root application component.
– Change Detection: Learn how Angular decides that a component property value has changed and when to update the screen
– Zones: Change Detection uses zones to intercept asynchronous activity and run its change detection strategies.
– Events: The DOM raises events. So can components and services.
– Router: With the Component Router service, users can navigate a multi-screen application in a familiar web browsing style using URLs.
– Forms: Support complex data entry scenarios with HTML-based validation and dirty checking.
– Http: Communicate with a server to get data, save data, and invoke server-side actions with this Angular HTTP client.
– Lifecycle Hooks: We can tap into key moments in the lifetime of a component, from its creation to its destruction, by implementing the “Lifecycle Hook” interfaces.
– Pipes: Services that transform values for display. We can put pipes in our templates to improve the user experience.
    price | currency:’USD’:true
– Testing: Angular provides a testing library for “unit testing” our application parts as they interact with the Angular framework.

### Author
Bhavin Patel

Happy Coding Smile

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