Dependency Injection Explained

In programming, a dependency is simply something a class or function needs to do its job. For example, a "Car" class might depend on an "Engine" class to run.

Manually creating these dependencies inside every class can lead to tightly coupled code. This makes your code harder to test, change, and reuse.

Dependency Injection (DI) helps us manage these relationships better, making our applications more flexible.

Inversion of Control (IoC) is a design principle where the flow of control is inverted. Instead of your code calling a library, a framework calls your code, managing object creation and lifecycle.

• Traditional: You go into the kitchen and cook your own meal (Your code creates its dependencies).
• IoC: You order from a menu, and the chef prepares and serves your meal (The framework creates and provides dependencies).

NestJS is built on IoC, meaning it takes responsibility for creating and managing many parts of your application.