Why Design Patterns?

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> Why Design Patterns?

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**Design Patterns have become an object of some controversy in the programming world in recent times, largely due to their perceived ‘over-use’ leading to code that can be harder to understand and manage.

It’s important to understand that Design Patterns were never meant to be hacked together shortcuts to be applied in a haphazard, ‘one-size-fits-all’ manner to your code. There is ultimately no substitute for genuine problem solving ability in software engineering.

The fact remains, however, that Design Patterns can be incredibly useful if used in the right situations and for the right reasons. When used strategically, they can make a programmer significantly more efficient by allowing them to avoid reinventing the proverbial wheel, instead using methods refined by others already. They also provide a useful common language to conceptualize repeated problems and solutions when discussing with others or managing code in larger teams.

That being said, an important caveat is to ensure that the how and the why behind each pattern is also understood by the developer.

Without further ado (in general order of importance, from most to least):

The Most Important Design Patterns
Singleton
The singleton pattern is used to limit creation of a class to only one object. This is beneficial when one (and only one) object is needed to coordinate actions across the system. There are several examples of where only a single instance of a class should exist, including caches, thread pools, and registries.

It’s trivial to initiate an object of a class — but how do we ensure that only one object ever gets created? The answer is to make the constructor ‘private’ to the class we intend to define as a singleton. That way, only the members of the class can access the private constructor and no one else.

Important consideration: It’s possible to subclass a singleton by making the constructor protected instead of private. This might be suitable under some circumstances. One approach taken in these scenarios is to create a register of singletons of the subclasses and the getInstance method can take in a parameter or use an environment variable to return the desired singleton. The registry then maintains a mapping of string names to singleton objects, which can be accessed as needed.