Book Image

Essential Angular

By : Victor Savkin, Jeff Cross
Book Image

Essential Angular

By: Victor Savkin, Jeff Cross

Overview of this book

Essential Angular is a concise, complete overview of the key aspects of Angular, written by two Angular core contributors. The book covers the framework's mental model, its API, and the design principles behind it. This book is fully up to date with the latest release of Angular. Essential Angular gives you a strong foundation in the core Angular technology. It will help you put all the concepts into the right places so you will have a good understanding of why the framework is the way it is. Read this book after you have toyed around with the framework, but before you embark on writing your first serious Angular application. This book covers concepts such as the differences between Just-In-Time (JIT) and Ahead-Of-Time (AOT) compilation in Angular, alongside NgModules, components and directives. It also goes into detail on Dependency Injection and Change Detection: essential skills for Angular developers to master. The book finishes with a look at testing, and how to integrate different testing methodologies in your Angular code.
Table of Contents (11 chapters)

Injector tree

Now you know that the dependency injection configuration has two parts:

  • Registering providers: How and where an object should be created.
  • Injecting dependencies: What an object depends on.

And everything an object depends on (services, directives, and elements) is injected into its constructor. To make this work the framework builds a tree of injectors.

First, every DOM element with a component or a directive on it gets an injector. This injector contains the component instance, all the providers registered by the component, and a few "local" objects (for example, the element).

Second, when bootstrapping an NgModule, Angular creates an injector using the module and the providers defined there.

So the injector tree of the application will look like this: