SWPatterns.com

Snapshot - Ruby

The Snapshot pattern allows saving and restoring the internal state of an object. This is useful for implementing features like undo/redo, checkpoints, or transaction rollback. The core idea is to encapsulate the object’s state into a separate snapshot object, enabling reverting to that saved state without …

Policy - Ruby

The Policy pattern encapsulates business rules and logic related to permissions and authorization within dedicated policy objects. This promotes separation of concerns, making the code more maintainable and testable. Instead of scattering authorization checks throughout the application, a central policy determines if …

Specification - Ruby

The Specification pattern allows you to define a set of rules (specifications) that an object must satisfy to be considered valid or to perform a specific action. Instead of scattering validation logic throughout your code, you encapsulate it within these reusable specification objects. This promotes cleaner, more …

Null Object - Ruby

The Null Object pattern provides a substitute for an object that would otherwise be null or undefined. This avoids null checks throughout the code, simplifying logic and reducing the risk of NoMethodError exceptions. The null object implements the expected interface but has a default or “do nothing” …

Visitor - Ruby

The Visitor pattern allows you to add new operations to a hierarchy of objects without modifying the objects themselves. It achieves this by defining a separate “visitor” class that implements the operation for each type of object in the hierarchy. The objects “accept” the visitor, allowing the …

Template Method - Ruby

The Template Method pattern defines the skeleton of an algorithm in a base class, deferring some steps to subclasses. It allows subclasses to redefine certain steps of an algorithm without changing the algorithm’s structure. This promotes code reuse and avoids duplication.

The Ruby code defines an abstract Report …

Strategy - Ruby

The Strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable. It allows an algorithm to vary independently from the clients that use it. Here, we define different shipping cost calculation strategies (e.g., for ground, air). The ShippingContext class accepts a strategy …

State - Ruby

The State pattern is a behavioral design pattern that lets an object alter its behavior when its internal state changes. It avoids using many conditional statements based on the object’s state by encapsulating each state into separate classes. The context object delegates the work to a state object, which …

Observer - Ruby

The Observer pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically. A subject (observable) maintains a list of observers and notifies them of any state changes. This promotes loose coupling as subjects don’t need …

Memento - Ruby

The Memento pattern captures and externalizes an object’s internal state so that the object can be restored to this state later, even if the object itself is modified or destroyed. This allows for “undo” operations or saving/restoring progress without violating encapsulation. My Ruby implementation uses a …