Crux of Design patterns

Gang of Four

This post’s purpose is to find the fundamental inextricable chord that connects almost or even all the design pattern under the bright blue sunny sky.  The fundamental high level mission or goal of the gamut of GOF Design Patterns are giving much needed flexibility, loose coupling and resilience to code and its sub structures.

>Introducing flexibility during static & runtime (aka Dynamic Flexibility):

                Polymorphic interface are the key for this type of flexible systems.  Let’s break this into nuts and bolts, and then smooth the surfaces by refinement. Interfaces(C#/JAVA) are contracts that lay boundaries or signature of methods/functions. This is akin to an abstract class with pure virtual/abstract methods. Modern programming languages have developed a special keyword that builds semantics behind them. That said and out of the way, we need to prove why using interface are dynamically flexible? Any line of code that has a “new” (JAVA/C#) keyword is prone for hardcoding the concrete class on either side of the equation. This is a humongous blunder and works against the flexibility of the code. Reminds me of the OOPS principle – “programming to interface rather than implementation”. WHY? When one puts concrete classes on the left side of the equation, then one cannot have the flexibility to change or switch the variable in context with other types of same nature. We introduce an inevitable, deliberate constraint.

Caffeine cup = new Caffeine ()  ; 

ICaffeine cup = new Caffeine () ; 

On the other hand if we follow the rule “programming to interfaces”, i.e., left side of the equation has a polymorphic interface. Now this allows as swapping during run time any other similar matching type. Popular examples are Strategy, Factory Method, Abstract Factory, Decorator, State, Composite, Command, Observer etc.

>Introducing flexibility during post production without redeployment:

                                                                I am not going to elaborate much on this front, as I have already covered in my previous blog post about IOC/DI. Please refer the post IOC/DI – From a Manager’s Perspective.