31/12/2022
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.
Factory Method
A normal factory produces goods; a software factory produces objects. And not just that — it does so without specifying the exact class of the object to be created. To accomplish this, objects are created by calling a factory method instead of calling a constructor.
Strategy
The strategy pattern allows grouping related algorithms under an abstraction, which allows switching out one algorithm or policy for another without modifying the client. Instead of directly implementing a single algorithm, the code receives runtime instructions specifying which of the group of algorithms to run.
Observer
This pattern is a one-to-many dependency between objects so that when one object changes state, all its dependents are notified. This is typically done by calling one of their methods.
Builder
As the name implies, a builder pattern is used to build objects. Sometimes, the objects we create can be complex, made up of several sub-objects or require an elaborate construction process. The exercise of creating complex types can be simplified by using the builder pattern.
Adapter
This allows incompatible classes to work together by converting the interface of one class into another. Think of it as a sort of translator: when two heads of states who don’t speak a common language meet, usually an interpreter sits between the two and translates the conversation, thus enabling communication.
