SWPatterns.com

Snapshot - Swift

The Snapshot pattern captures and restores the state of an object, allowing for easy undo/redo functionality or saving/loading of progress. It’s implemented here using Swift’s Codable protocol to serialize the object’s state into a snapshot (a dictionary in this case). The takeSnapshot() method …

Policy - Swift

The Policy pattern allows you to encapsulate a complex set of business rules into separate, interchangeable policy objects. This promotes flexibility and maintainability by avoiding monolithic conditional logic. Instead of a single class making decisions based on numerous if/else statements, different policies can be …

Specification - Swift

The Specification pattern decouples the construction of a complex object from its representation. It defines a class that represents the desired properties of an object, and separate “builder” classes that implement these specifications to create the object. This promotes flexibility and allows for creating …

Null Object - Swift

The Null Object pattern provides a substitute for a null reference or nil value, allowing you to avoid null checks throughout your code. Instead of checking for nil, you call a method on the null object, which performs a no-op or returns a default value. This simplifies code and reduces the risk of …

Visitor - Swift

The Visitor pattern allows you to define a new operation without modifying the classes of the objects on which it operates. It’s achieved by moving the operation to a separate “visitor” class that accepts different object types as arguments. This is useful when you have a complex object structure and …

Template Method - Swift

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 Swift example defines a …

Strategy - Swift

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. In this Swift implementation, we define a protocol SortingStrategy with a single method sort. Different concrete strategies like …

State - Swift

The State pattern is a behavioral pattern that allows an object to alter its behavior when its internal state changes. Instead of implementing state-specific logic within a single class using conditional statements, the pattern creates separate state classes to encapsulate each behavior. A context class holds a …

Observer - Swift

The Observer pattern defines a one-to-many dependency between objects. When the state of one object (the subject) changes, all its dependent objects (the observers) are notified and updated automatically. This promotes loose coupling, allowing subjects and observers to interact without knowing each other’s …

Memento - Swift

The Memento pattern is a behavioral design pattern that allows capturing and externalizing the internal state of an object without violating encapsulation. This is useful for implementing undo/redo functionality or saving/restoring object states. The pattern defines three roles: the Originator holds the state, the …