Dependency Injection

This article discusses Dependency Injection as a design pattern and as a part of the SOLID principles.

Dependency Injection is a software design pattern. In other words, it is a technique of structuring the code of an application. The technique implements inversion of control.

Dependency Injection is also a principle belonging to the set called SOLID:

• Single Responsibility Principle (SRP)
• Open Closed Principle (OCP)
• Liskov Substitution Principle (LSP)
• Interface Segregation Principle (ISP)
• Dependency Injection (DI)
• Inversion of Control (IoC)
• Dependency Inversion Principle (DIP) 

Most often, however, DI is regarded as a realization of the IoC paradigm.

Dependency Injection allows us to create code which is loosely coupled. This term is best understood by defining its opposite: tight (or heavy) coupling. In computer software, tight coupling means that the software is dependant on other software in order to work properly.