Class Diagram Example: GoF Design Patterns - Singleton

Description:

Singleton design pattern is one of the Gang of Four (GOF) design patterns. Singleton design pattern ensures that only one instance of a class is allowed within a system.

Get started with this Singleton pattern template. Click Use this Template to start.

What is Class Diagram?

A Class is a blueprint that is used to create Object. The Class defines what object can do. Class Diagram gives the static view of an application. Class diagrams are at the heart of UML. They are based on the principles of object orientation and can be implemented in various phases of a project. A class diagram describes the types of objects in the system and the different types of relationships that exist among them. UML Class Diagram gives an overview of a software system by displaying classes, attributes, operations, and their relationships. Class Diagram can also help to construct the code for the software application development.

Guidelines for creating Class Diagram?

  1. Identify classes
    • a. From domain analysis such as textual analysis
    • b. From CRC cards
    • c. From use case description
    • d. From sequence diagram or use case scenarios
  2. Give analysis a name and a brief description which could be done through terms and glossary
  3. Structure classes in the right places of the diagram and related them with simple relationships
  4. As the development move forward, detail the class with attributes and operations, this often done in conjunction with use case and sequence diagrams
  5. Refine the class diagram with inheritance for future reuse
  6. Elaborate the details which is helpful for implementation such as accessibility, rules, constraints and etc.
  7. Put related classes into packages to form your software architecture

When to use Class Diagram?

As a sketch:

  • Perform visual modeling rather than lengthy textual description
  • Casually use for illustrate initially ideas develop without the need of upfront requirement documentation
  • Instant revise from code to class diagram to pinpoint a specific problem
  • Used it to visual model to get rough selective ideas just in time whenever needed

As a blueprint:

  • a complete design to be implemented
  • typically done with a proper UML modeling tools

As code engineering:

  • Perform model to code forward engineering
  • Perform code to model reverse engineering
  • Keep code and model in sync by performing round-trip engineering

As data engineering:

  • Design data modeling based on detailed class diagram
  • Reverse class or object wrapper base on database
  • Use database framework such as Hibernate ORM Framework

As Web API generation

  • Generate web API based on Class Diagram such as SWAGGER

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