Communication between collaborating directives in Angular

What if a complicated component comes along that is naturally modeled by multiple directives? This group of directives, as a whole, form a single self contained component. None of directives in the group can stand alone because they only make sense when used together; they collaborate; they are aware of each other and need to communicate with each other.

This post will discuss best practices for managing communication among collaborating directives and illustrate these practices with an example.