Builder Pattern extracts the construction of a complex object from its user.
DeliveryBuilder exposes AddPackage to accumulate packages into a delivery
and exposes Build() to return the packed delivery.
Few online examples - such as
geeksforgeeks -
advocate the builder pattern help build different child objects with the same
build interface. E.g. VehicleBuilder is implemented by CarBuilder and
BusBuilder which builds Car and Bus. The caller - YourBoss - takes
whatever VehicleBuilder generates and starts to use it.
I disagree the above example is the main point of the builder pattern but the
use of abstraction in general. The above example simply says YourBoss can use
an object without knowing its concreate implementation. And, the object happened
to be the builders. On the other hand, the point of builder pattern is about
moving complex code for object construction into a standalone component.
Both Builder and Abstract Factory extract the construction code into a single place. The responder of a stackoverflow post explained the difference very well: "the Builder is only needed when an object cannot be produced in one step."
I agree with the above statement. Many builder examples I found online (e.g. RIP tutorial) simply takes a variable and passes it to the object as a member variable - which I think the target object should just take the variables as constructor parameters instead.
- https://refactoring.guru/design-patterns/builder
- https://www.geeksforgeeks.org/builder-design-pattern/
- https://stackoverflow.com/questions/757743/what-is-the-difference-between-builder-design-pattern-and-factory-design-pattern
- https://riptutorial.com/cplusplus/example/30166/builder-pattern-with-fluent-api