builderpatterns

The Builder pattern, sometimes written as the builder pattern or builder patterns, is a creational design pattern that provides a way to construct a complex object step by step, separating the construction process from the final representation. This separation allows the same construction steps to produce different representations of an object.

Core components typically include a Builder interface, which declares methods for creating parts of the product; a ConcreteBuilder, which implements the steps and maintains a reference to the product; the Product, which represents the complex object under construction; and a Director, which encapsulates a construction sequence. Clients usually use a builder to assemble the product, often through a fluent interface, and then retrieve the finished product.

When to use: the pattern is suitable when an object has many optional parts or configuration options, when construction must follow a specific sequence, or when you want to separate the construction of a complex object from its representation so you can create different representations with the same process. Benefits include clearer construction logic and the ability to create immutable products; drawbacks include additional classes and potential over-engineering for simple objects.

Variants and related ideas: Fluent builders employ method chaining to improve readability; Step Builder enforces a sequence of required steps to prevent invalid configurations. Some implementations use an inner builder. The Builder pattern is distinct from the telescoping constructor anti-pattern and is related to other creational patterns such as Abstract Factory and Factory Method.

History and usage: The pattern was described in the Gang of Four design patterns book (1994) and has since become common in object-oriented languages for configuring complex objects and object graphs in a readable, maintainable way.