Builder Design Pattern in Software Development
The Builder Design pattern is a creational design pattern.
Purpose:
The intent is to separate complex object creation from its representation, so that the same construction process can create different representations.
In other words, the pattern allows you to produce different types and representations of an object using the same construction code.
Explanation:
The Builder design pattern suggests that you extract the object construction code out of its own class and move it to separate objects called builders.
The builder design pattern doesn’t require products to have a common interface.
It allows to create complex objects step by step using the correct sequence of actions.
The Builder doesn’t allow other objects to access the product while it’s being built.
The construction is controlled by a director object that only needs to know the type of object it is to create.
Advantages:
I. Promotes Single Responsibility Principle. You can isolate complex construction code from the business logic of the product. Provides a clear separation between the construction and representation of an object.
II. Provides better control over construction process.
III. Supports to change the internal representation of objects.
IV. The pattern encourages separation of concerns and promotes application extensibility.
UML Class Diagram:
Participants/Components:
The Builder Pattern is comprised of four components:
1. A builder interface — defines a template for the steps to construct the product.
2. A concrete builder — implements the builder interface and provides an interface for getting the product.
3. A director — constructs the object through the builder interface.
4. A product — the end object that’s constructed.
Real-world code in C#:
Usage:
It should be used in following cases:
a. When it’s necessary to use a constructor with a long parameter list.
b. When there’s a long list of constructors with different parameters.
c. When it’s necessary to build different representations of the same object.
Related Patterns:
1. A Factory Design Pattern is used when the entire object can be easily created, and object is not very complex, whereas a Builder Pattern is used when the construction process of a complete object is very complex.
2. Many designs start by using Factory Method (less complicated and more customizable via subclasses) and evolve toward Abstract Factory, Prototype, or Builder (more flexible, but more complicated).
3. You can use Builder when creating complex Composite trees because you can program its construction steps to work recursively.
4. You can combine Builder with Bridge: the director class plays the role of the abstraction, while different builders act as implementations.
5. Abstract Factories, Builders and Prototypes can all be implemented as Singletons.
Real-world implementations of Builder classes in the .NET framework:
1. ConnectionStringBuilder
2. UriBuilder
3. StringBuilder
References:
