Dependency Inversion

Dependency Inversion Is About Source Code Direction

A business rule often starts simple and then becomes tied to a database client, email library, payment SDK, filesystem API, or framework object. The code still works, but changing the technical detail now forces changes into the code that expresses the business decision. Dependency inversion addresses this coupling. Its central idea is easy to miss: the important question is not merely whether an interface exists. The important question is which code defines the abstraction and which code depends on it.