link: SOLID
Dependency Inversion Principle
Overview
High-level modules should not be dependent on low-level modules; both should rely on abstractions. Additionally, these abstractions should not be based on details; rather, the details should be based on abstractions.
The Dependency Inversion Principle (DIP) is crucial for building software that’s modular and simple to maintain. It guides the development of a system where different parts are not tightly connected but can work together through abstract interfaces. This means that the main logic of the program doesn’t depend on the nitty-gritty details of how things are done at a lower level.
Content
Principle Explained
The principle distinguishes between two types of classes:
- High-Level Modules: Contain complex business logic that directs low-level classes to do something.
- Low-Level Modules: Implement basic operations such as working with a disk, transferring data over a network, connecting to a database, etc.
To ensure compliance with DIP follow this rules:
- High-level modules should not depend on low-level modules. Both should depend on abstractions.
- Abstractions should not depend on details. Details should depend on abstractions.
Practical Example
BEFORE
Initially, a high-level module is directly dependent on a low-level module, leading to a rigid and fragile structure that is challenging to test and maintain.
AFTER
By inverting the dependency, both high-level and low-level modules rely on shared abstractions. This results in a more flexible and maintainable system where changes to low-level details have minimal impact on high-level modules.
This approach not only enhances code reusability and maintainability but also simplifies unit testing by allowing for easy mocking or stubbing of the lower-level components.
Summary
Summary
Following the Dependency Inversion Principle brings flexibility and easier maintenance to software systems. It encourages a setup where the core business logic is neatly separated from the technical details of how things are done. This separation is crucial for a well-designed application.