Lesson 6 - Passing dependencies with Dependency Injection
Software design Software architectures and dependency injection Passing dependencies with Dependency Injection
In the previous lesson, Wrong ways of passing dependencies - Singleton and SL, we completed a walk through the wrong ways of passing dependencies in multi-tier applications. Overall, it was about using any static class members, including Singleton, but also about passing dependencies through a container, known as the Service Locator pattern, or different variations of these approaches. Today, we're gonna show how to do it right on our car example as always.
Laborious ways
So far, the only right way we know is to pass dependencies manually one by
one. This is also the approach we showed at the very beginning of the course. We
created a database instance in index.php and passed it to the controller and
through the controller to the model where it was needed. Although this approach
is correct from the software-design point of view, you can certainly imagine how
much work it would take to pass several dependencies like this even in a
medium-sized application. And since controllers are created automatically by the
router, we 'd also need to identify which dependencies should be passed to which
controller. Last time, I promised I would stop bothering you with the wrong
solutions and questions any more. Today's lessons will bring answers to
everything. Really 
What was wrong?
In all the presented solutions, we tried to hack the code so we didn't have to pass dependencies. This CANNOT be achieved without negative impacts. All such attempts will always result in failures. If we don't pass
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Wrong ways of passing dependencies - Singleton and SL
Software architectures and dependency injection
IoC container source code