Dev MaxxingIntermediateSoftware Design75 sec

Dependency injection

Dependency injection is supplying a piece of code with the other components it needs from outside, rather than having it create or look up those components itself.

Mark as completed

Prerequisite: Separation of concerns

What matters

Because dependencies come from outside, they can be swapped, such as for a test double during testing, without changing the code that uses them.

Example

Passing a database connection into a function as a parameter, rather than the function creating its own connection internally, is dependency injection.

Common misconception

Dependency injection is not a specific tool or framework feature; it's a general principle that can be applied with or without any special library support.

Recall question

What does dependency injection make easier to swap during testing?

Keywords and related concepts