Catalog
concept#Architecture#Software Engineering#Object Oriented#Programming Principles

SOLID Principles

The SOLID principles are five fundamental principles of object-oriented programming that help make software more maintainable and flexible.

The SOLID principles are a set of five design principles formulated by Robert C.
Established
Medium

Classification

  • Medium
  • Technical
  • Design
  • Advanced

Technical context

Integration of testing frameworks.Use of CI/CD pipelines.Integration with project management tools.

Principles & goals

Single Responsibility PrincipleOpen/Closed PrincipleLiskov Substitution PrincipleInterface Segregation PrincipleDependency Inversion Principle
Build
Domain, Team

Use cases & scenarios

Compromises

  • Misunderstandings in the application of the principles.
  • Resistance within the team against changes.
  • Lack of documentation of the principles in the project.
  • Conduct regular code reviews.
  • Document the principles in the project.
  • Gather feedback from team members.

I/O & resources

  • Software Requirements
  • Existing Codebase
  • Development Team
  • Maintainable and Extensible Software
  • Reduced Technical Debt
  • Higher Code Quality

Description

The SOLID principles are a set of five design principles formulated by Robert C. Martin. They aim to increase the maintainability and flexibility of software by providing clear guidelines for structuring classes and their interactions. These principles are: Single Responsibility Principle (SRP), Open/Closed Principle (OCP), Liskov Substitution Principle (LSP), Interface Segregation Principle (ISP), and Dependency Inversion Principle (DIP).

✔

  • Increased maintainability of the software.
  • Better testability through clear interfaces.
  • Easier extensibility and adaptation.

✖

  • Can lead to over-complexity if applied excessively.
  • Requires a certain level of experience within the team.
  • Not all problems require the application of all principles.

  • Code Quality

    Measurement of the maintainability and readability of the code.

  • Error Rate

    Number of errors per 1000 lines of code.

  • Development Time

    Time required to implement new features.

E-Commerce Application

An e-commerce application that applies the SOLID principles to ensure a clear separation between different components such as product management, order processing, and user management.

Banking Application

A banking application that uses SOLID principles to enhance the security and maintainability of the software by defining clear interfaces and responsibilities.

Social Networking Platform

A social networking platform that implements SOLID principles to ensure the extensibility and adaptability of the platform.

1

Train the team on the SOLID principles.

2

Analyze the existing codebase.

3

Apply the principles when developing new features.

⚠️ Technical debt & bottlenecks

  • Technical debt due to neglecting the SOLID principles.
  • Growth of complexity due to insufficient modularity.
  • Maintenance difficulties due to undocumented decisions.
Over ComplexityResistance to ChangeLack of Documentation
  • A developer ignores the Single Responsibility Principle and adds multiple responsibilities to a class.
  • A team does not use the Open/Closed Principle and modifies existing classes instead of creating new ones.
  • A project lacks clear documentation of the principles applied.
  • Assuming that all principles must be applied in every case.
  • Believing that applying the principles will yield immediate results.
  • Underestimating the need for training.
Knowledge of object-oriented programming.Experience with software architecture.Ability to work in teams and communicate.
ModularityMaintainabilityExtensibility
  • • Technical limitations of the platform.
  • • Resource constraints within the team.
  • • Regulatory requirements.