This course will teach you the ins and outs of dependency injection in Angular 2. You will learn what dependency injection means, how it applies to software in general and how it is implemented in Angular 2. We will take a look at simple use cases like injecting services, to exploring different providers recipes and when they are useful. We will also cover almost unknown features like viewProviders, OpaqueToken and edge cases where forwardRef() is needed.

This Angular 2 course assumes knowledge of some fundamentals.
We have an Angular 2 course that will [Get you started](https://egghead.io/series/angular-2-fundamentals)

To get started with Dependency Injection, we first want to understand what it is actually all about. In this lesson, we take a look at Dependency Injection as a software design pattern and clarify why it is so useful that Angular implements a system for it.

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Understand Angular Dependency Injection

This lesson explains how we can inject simple service dependencies into Angular 2 components using providers. We’ll also discuss what providers are and why they are needed.

Inject an Angular Service into a Component using Providers

In this lesson, we’re going to take a look at how adding the class provide to the providers property of a component to create an actual provider. We’ll learn what a provider specifically does and how we can provide different dependencies with the same token.

Use Provide and UseClass in Angular Providers

In this lesson, we discuss how and when to use factory providers, to enable dependencies that shouldn’t be available to Angular’s DI.

Use Angular Factory Providers

This lesson discusses when and how to add dependencies, resolved by Angular’s DI, to factory providers. The example used in this lesson builts upon the previous lesson on understanding factory providers.

Use Angular Factory Providers with dependencies

In order to resolve a dependency, Angular’s DI uses type annotations. To make sure these types are preserved when transpiled to ES5, TypeScript emits metadata. In this lesson we’ll explore how the @Injectable decorator ensures metadata generation for services that have their own dependencies.

Understand Angular @Injectable

Dependecies aren’t always objects created by classes or factory functions. Sometimes, all we really want is inject a simple value, which can be a primitive, or maybe just a configuration object. For these cases, we can use value providers and in this lesson we’ll discuss, how they are created.

Use Angular Value Providers

When using provider string tokens, there’s a chance they collide with other third-party tokens. Angular has with the concept of opaque tokens, that allow us to make whatever token we use unique, so we don’t run into collision problems. In this lesson we’ll explore how they work.

Angular 2 Dependency Injection (DI) Explained

Pascal Precht

Course Content