AngularJS Essentials

Dependency Injection
and Services
Cohesion is one of the most important and perhaps overlooked concepts of the
object-oriented programming paradigm. It refers to the responsibility of each part of
the software. No matter which component we talk about, every time it implements
behavior different from its responsibilities, cohesion is degraded.
Low cohesion applications contain plenty of duplicated code and are hard to unit
test because it is difficult to isolate the behavior, which is usually hidden inside the
component. It also reduces the reuse opportunities, demanding much more effort to
implement the same thing several times. In the long term, the productivity decreases
while the maintenance costs are raised.
With AngularJS, we are able to create services, isolating the business logic of every
component of our application. Also, we can use the framework's dependency
injection mechanism to easily supply any component with a desired dependency.
The framework also comes with a bunch of built-in services, which are very useful in
daily development.
In this chapter, we'll be covering the following topics:
• Dependency injection
• Creating services
• Using AngularJS built-in services
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