When to use Dependency Injection

Question

I\'ve had a certain feeling these last couple of days that dependency-injection should really be called \"I can\'t make up my mind\"-pattern. I know this might sound silly,

Answer 1

DI is very useful for decoupling your system. If all you're using it for is to decouple the database implementation from the rest of your application, then either your application is pretty simple or you need to do a lot more analysis on the problem domain and discover what components within your problem domain are the most likely to change and the components within your system that have a large amount of coupling.

DI is most useful when you're aiming for code reuse, versatility and robustness to changes in your problem domain.

How relevant it is to your project depends upon the expected lifespan of your code. Depending on the type of work you're doing zero reuse from one project to the next for the majority of code you're writing might actually be quite acceptable.

An example for use the use of DI is in creating an application that can be deployed for several clients using DI to inject customisations for the client, which could also be described as the GOF Strategy pattern. Many of the GOF patterns can be facilitated with the use of a DI framework.

DI is more relevant to Enterprise application development in which you have a large amount of code, complicated business requirements and an expectation (or hope) that the system will be maintained for many years or decades.