Wrapper

Wrap an object to enable decoration

A wrapper, as the name suggest, wraps an object or a value. To this regard, it is a generalization of the Value Object.

But the Wrapper exposes a single method such as expose and enable composition to perform operations on objects.

Using wrappers allow to pick specific decorators for the task at hand, in which each decorator is a Compute Object, except for the wrapped value which often is a Value Object.

interface IWrapped<T> {
  expose(): T;
}

class Identity<T> implements IWrapped<T> {
  constructor(private readonly value: T) {}
  expose() {
    return this.value;
  }
}

abstract class Wrapper<T> implements IWrapped<T> {
  constructor(protected readonly value: IWrapped<T>) {}
  abstract expose(): T;
}

class LowerCase extends Wrapper<string> {
  expose() {
    return this.value.expose().toLowerCase();
  }
}

class Slugify extends Wrapper<string> {
  expose() {
    return this.value
      .expose()
      .replace(' ', '-')
      .replace(/[^a-zA-Z0-9-]/g, '');
  }
}

const result = 
    new Slugify(
        new LowerCase(
            new Identity('Hello World')
        ),
    ).expose();

expect(result).toBe('hello-world');