builder

Builder

Intent

Separate the construction of a complex pbject from its representation so that the same construction process can create different representations

Also Known As

Fluent API

Applicability

Use the Builder pattern when:

• the algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
• the construction process must allow different representations for the object that's constructed

Participants

• Builder (TextConverter)
  • specifies an abstract interface for creating parts of a Product object
• ConcreteBuilder (ASCIIConverter, TeXConverter, TextWidgetConverter)
  • constructs and assembles parts of the product by implementing the Builder interface
  • defines and keeps track of the representation it creates
  • provides an interface for retrieving the product (e.g., GetASCIIText, GetTextWidget)
• Director (RTFReader)
  • constructs an object using the Builder interface
• Product (ASCIIText, TeXText, TextWidget)
  • represents the complex object under construction. ConcreteBuilder builds the product's internal representation and defines the process by which it's assembled
  • includes classes that define the constituent parts, including interfaces for assembling the parts into the final result

Related Patterns

Abstract Factory is similar to Builder in that it too may construct complex objects. The primary difference is that the Builder pattern focuses on constructing a complex object step by step. Abstract Factory's emphasis is on families of product objects (either simple or complex). Builder returns the product as a final step, but as far as the Abstract Factory pattern is concerned, the product gets returned immediately.
A Composite is what the builder often returns.