The facade pattern
As systems evolve, they can get very complex. It is not unusual to end up with a very large (and sometimes confusing) collection of classes and interactions. In many cases, we don’t want to expose this complexity to the client. This is where our next structural pattern comes to the rescue: facade.
The facade design pattern helps us hide the internal complexity of our systems and expose only what is necessary to the client through a simplified interface. In essence, facade is an abstraction layer implemented over an existing complex system.
Let’s take the example of the computer to illustrate things. A computer is a complex machine that depends on several parts to be fully functional. To keep things simple, the word “computer,” in this case, refers to an IBM derivative that uses a von Neumann architecture. Booting a computer is a particularly complex procedure. The CPU, main memory, and hard disk need to be up and running, the boot...
