How dependencies are provided.
WHAT IT IS
A mechanism that creates objects and supplies what they need.
WHAT THAT MEANS PRACTICALLY
You declare what a class requires, and it is provided automatically.
WHY THAT MATTERS
Classes do not create their own dependencies, so those can be substituted.
WHAT THAT ENABLES
Testing, by supplying a substitute Changing an implementation without editing everything using it
WHAT BINDING MEANS
Telling the container how to construct something, or which implementation to use for an interface.
WHERE THAT IS DONE
In service providers, which run at startup.
WHAT SERVICE PROVIDERS DO
Register bindings and perform startup configuration.
WHAT FACADES ARE
A concise way of reaching services in the container.
WHAT TO KNOW ABOUT THEM
Convenient, and they obscure dependencies.
WHAT TO PREFER IN CLASSES YOU WILL TEST
Declared dependencies, provided by the container.
WHAT TO AVOID
Reaching for services from deep inside classes Binding things that do not need binding
