Understanding Dependency Injection with Chicken Cutlets

#beginners

The Backstory

So I started a new job. I'm learning a new programming language and framework. And my brain is fried.

As a form of stress relief, I spent the entirety of my lunch breaks obsessively watching Nigella Lawson's cooking shows - without the intention of following her recipes, of course! During this past week, I also needed to understand the concept of dependency injection to complete my day-to-day work. By doing both things at the same time, I ended up understanding dependency injection by frying my brain... and some chicken cutlets.

Let's Get Cooking

At a minimum, I'll need:

2 chicken escalopes
1 egg

Well, I could get these ingredients by farming some chickens and harvesting eggs in my backyard. But, what if I suddenly decided to cook with another breed of chickens? I can't just trade my whole flock of chickens for another! That would be a disaster!

Instead of farming my own chickens, why don't I buy some chickens from the farmer's market? I'm now free to switch between chicken breeds whenever I like! Plus, I don't have the hassle of rearing chickens in my nonexistent backyard.

In the programming world, this concept is called inversion of control, or IoC for short. I don't have control over growing my own chickens, because I hate the idea of opening a chicken farm. Instead, I'm delegating that task to other farmers, so all I have to do is buy their produce. I make sure to only do one thing: cook the chickens.

Dependency injection, in this example, refers to the act of buying chicken escalopes from the farmer's market and then "injecting" that ready-made ingredient into our cooking, instead of making it from scratch.

And that's it! Now, it's time to eat.