Revisions

_posts/06-01-01-Dependency-Injection.md

@@ -4,5 +4,10 @@ title: Dependency Injection
 
 # Dependency Injection {#dependency_injection_title}
 
-Dependency Injection is a basic concept that solves a complex problem. As a software design pattern it is being adopted in 
-some way or another by all major PHP projects.
+From [Wikipedia](http://en.wikipedia.org/wiki/Dependency_injection):
+
+> Dependency injection is a software design pattern that allows the removal of hard-coded dependencies and makes it 
+> possible to change them, whether at run-time or compile-time.
+
+This quote makes the concept sound much more complicated than it actually is. Dependency Injection is providing a component 
+with it's dependencies either through constructor injection, method calls or the setting of properties. It is that simple.

_posts/06-02-01-Basic-Concept.md

@@ -4,15 +4,11 @@ isChild: true
 
 ## Basic Concept {#basic_concept_title}
 
-From [Wikipedia](http://en.wikipedia.org/wiki/Dependency_injection):
+We can demonstrate the concept with a simple, yet naive.
 
-> Dependency injection is a software design pattern that allows the removal of hard-coded dependencies and makes it 
-> possible to change them, whether at run-time or compile-time.
-
-This quote makes the concept sound much more complicated than it actually is. Dependency Injection is providing a component 
-with it's dependencies either through constructor injection, method calls or the setting of properties. It is that simple.
-
-We can demonstrate the concept with a simple, yet naive, example.
+Here we have a `Database` class that requires an adapter to speak to the database. We instantiate the 
+adapter in the constructor and create a hard dependency. This makes testing difficult and means the `Database` class is 
+very tightly coupled to the adapter.
 
 {% highlight php %}
 <?php
@@ -31,9 +27,7 @@ class Database
 class MysqlAdapter {}
 {% endhighlight %}
 
-Here we have a `Database` class that requires an adapter to speak to the database. We instantiate the 
-adapter in the constructor and create a hard dependency. This code can be refactored to use Dependency Injection 
-and therefore loosen the dependency.
+This code can be refactored to use Dependency Injection and therefore loosen the dependency.
 
 {% highlight php %}
 <?php

_posts/06-03-01-Complex-Problem.md

@@ -5,7 +5,12 @@ isChild: true
 ## Complex Problem {#complex_problem_title}
 
 If you have ever read about Dependency Injection then you have probably seen the terms *"Inversion of Control"* or *"Dependency Inversion Principle"*. 
-These are the complex problems that Dependency Injection solves, or to be more precise, elegantly solves.
+These are the complex problems that Dependency Injection solves.
+
+### Inversion of Control
+
+Inversion of Control is as it says, "inverting the control" of a system by keeping organisational control entirely separate from our objects. 
+In terms of Dependency Injection, this means loosening our dependencies by controlling and instantiating them elsewhere in the system.
 
 For years, PHP frameworks have been achieving Inversion of Control, however, the question became, which part of control 
 are you inverting, and where to? For example, MVC frameworks would generally provide a super object or base controller that other 
@@ -15,6 +20,8 @@ dependencies, this method simply moved them.
 Dependency Injection allows us to more elegantly solve this problem by only injecting the dependencies we need, when we need them, 
 without the need for any hard coded dependencies at all.
 
+### Dependency Inversion Principle
+
 Dependency Inversion Principle is the "D" in the S.O.L.I.D set of object oriented design principles that states one should 
 *"Depend on Abstractions. Do not depend on concretions."*. Put simply, this means our dependencies should be interfaces/contracts or abstract 
 classes rather than concrete implementations. We can easily refactor the above example to follow this principle.