In this new post to the QaFoo blog they talk about a common pattern in framework development - the injection of a dependency injection container - and, more specifically, the ContainerAware interface in the Symfony2 framework and why it's "considered harmful".

The ContainerAware interface (actually ContainerAwareInterface, ContainerAware is a basic implementation of it) is part of the Symfony2 API, but a similar concept is known from many other frameworks and many applications rely on it. It defines only the one method setContainer(), which allows to inject the DIC into into an object so that it can directly retrieve services from it. [...Issues with it include the fact that] accessing the DIC in your classes can seriously harm maintainability and code re-usability in the long run.

They talk about three things specifically that using this sort of development pattern can cause in your application:

• Reduced testability
• Hidden dependencies (harder to see when a class has too many)
• Feature sneak-in (that could promote bad usage practices)