# Decorator

## About

* To extend an object, without changing the original object implementation.
* Is used for the `O` of `SOLID`.
  * Open to extension, Closed to modification.
* Ex.: You make the `DecoratedComponent` implement the same interface as the object you want to extend. And in the `DecoretedComponent` `constructor` you pass the original component as an argument.

```typescript
class DecoratedComponent implements SomeObject {
	constructor (readonly obj: SomeObject) {
	}

	someFunc() {
		[extendDoingMoreStuff]
		...
		return this.obj.func()
	}
}
```

$$Decorator \neq Middleware$$, since middle kind of chains the layers in an array, and the decorators chains them kind of like recursively, one is inside of the other.