Builder

While Factory Patterns expose the internal components (such as the payload and stages of a rocket), the Builder Pattern encapsulates them by exposing only the building steps and provides the final products directly. At the same time, the Builder Pattern also encapsulates the internal structures of a product. This makes it possible for a more flexible abstraction and implementation of building complex objects.

The Builder Pattern also introduces a new role called director, as shown in the following diagram. It is quite like the client in the Abstract Factory Pattern, although it cares only about build steps or pipelines:

Now the only constraint from RocketBuilder that applies to a product of its subclass is the overall shape of a Rocket. This might not bring a lot of benefits with the Rocket interface we previously defined, which exposes some details of the rocket that the clients (by clients I mean those who want to send their satellites or other kinds of payload to space)...