Usefall

Purpose

A complex thing needs to be created.

I want to simplify its creation.

Leopard

I really want to build a fancy house but it’s too complicated!

class House {
  construct(material, doors, windows) {
    this.material = material;
    this.doors = doors;
    this.windows = windows;
  }
}

Leopard

Lightning Sloth, please help me!

Lightning Sloth

Sure. Describe the house you want to me.

class LightningSlothTheBuilder {
  houseMaterial;
  doors = [];
  windows = [];

  madeOf(material) {
    this.houseMaterial = material;
    return this;
  }

  withDoor(material) {
    this.doors.push(new Door(material));
    return this;
  }

  withWindow(material) {
    this.windows.push(new Window(material));
    return this;
  }
}

Leopard

The house should be made of dirt.

It should have a door made of diamond.

It should have a door made of emerald.

It should have a window made of steel.

const lightningSlothTheBuilder = new LightningSlothTheBuilder();

const leopardHouse = lightningSlothTheHouseBuilder
  .houseMaterial("dirt")
  .withDoor("diamond")
  .withDoor("emerald")
  .withWindow("steel");

Lightning Sloth

All done!

Leopard

What!? How did you finish so fast!?

Lightning Sloth

I focused on noting down all the things you described,

gradually, one by one, step by step.

Everytime I noted something down,

I returned myself so I can note the next thing.

Then I finally built the house.

Leopard

Wow thanks! You are so cool!

Lightning Sloth

I know. Sometimes you gotta go slow to go fast. Hehe.

Solution

Have a separate thing gradually handle object creation (a builder).

Gradually describe all the parts that are needed to the builder, finally tell the builder to create the thing you want.