Hello, developers! Today, let’s deep-dive into the labyrinthine world of Dependency Injection (DI) in Angular. If you’re looking to write Angular code that’s clean, modular, and easy to test, understanding Dependency Injection is essential. This article serves as a comprehensive guide on advanced techniques to expand your toolkit beyond basic DI methods.

A Quick Refresher on Angular’s Dependency Injection

Before we explore the advanced terrains, let’s revisit the basics of Dependency Injection in Angular. The fundamental idea is to define dependencies for components, services, or other classes and let Angular manage the lifecycle and provision of those dependencies.

Here’s a simple code snippet for a basic service:

To inject this service into a component, your code would look something like this:

Alright, ready for the advanced techniques? Let’s go!

1. Multi Providers

Ever found yourself needing multiple instances of a dependency? Angular gives you a nifty solution for this via the multi: true option. It lets you map multiple values or instances to a single token. This is especially useful when you want to offer an extensible API or gather multiple configurations under a single token.

Here’s how you can define multi providers: