Role

The Builder pattern separates the specification of a complex object from its actual construction. 

The same construction process can create different representations.

Intent

• Defines an instance for creating an object but letting subclasses decide which class to instantiate
• Refers to the newly created object through a common interface

Design

Main Players

• IBuilder
  • An interface defining what can be built
• Director
  • A sequence of operations that can be followed to create a Product
• Builder
  • A class that is called by a Director to make Product parts
• Product
  • The object under construction, by parts

Example Class Diagram

Demo Source Code (Git)

Advantage of the Builder/Director partnership

Products do not all necessarily turn out the same.

TheBuilder can redefine the way it works and, even with the sameDirector, produce a different product.

Furthermore, the Builder pattern constructs the product step by step under the director’s control.

Use the Builder pattern when…

• The object to be assembled might have different representations.
• You need fine control over the construction process.

Comparison with

Abstract Factory

Resources

• Pluralsight Design Patterns Library Course
• oodesign.com
• C# 3.0 Design Patterns
  • By Judith BISHOP
  • Publisher: O'Reilly Media

thanks....

@brs_snmz