eleev/swift-design-patterns

This system is a Swift-based library of design pattern implementations, serving as a practical reference for software engineering concepts. It provides runnable Swift playgrounds and documentation for a wide range of creational, behavioral, and structural patterns, including Singleton, Factory, Observer, and Adapter. The collection also covers concurrency patterns and specific Swift language features, offering concrete examples for each. The project has been refactored to remove legacy iOS boilerplate, focusing entirely on the pattern examples.

Added a new entry for the Factory Method creational design pattern, including a Markdown guide and a Swift playground. The documentation explains how to hide object creation logic and decouple code by using a factory class that returns different car types (Bugaggi, Fodr, Truck) based on a price tier. The accompanying Swift code demonstrates the pattern with a Car protocol, concrete car structs, and a CarFactory that selects the appropriate car type at runtime.

Common Design Patterns/Creational/FactoryMethod · high confidence

Added a new entry for the Lazy Initialization creational design pattern, including a Markdown guide and a Swift playground demonstrating delayed initialization of UI controls and data sources using the \lazy\ keyword and closures.

Common Design Patterns/Creational/LazyInitialization · high confidence

A new entry for the Bridge structural design pattern has been added to the documentation, explaining how to decouple an abstraction from its implementation to allow both to vary independently. The update includes a complete Swift code example demonstrating the pattern using mobile phone and charger hierarchies, along with a playground file to run the code interactively.

Common Design Patterns/Structural/Bridge · high confidence

The Coordinator structural design pattern is now available as a new example, including a Markdown documentation file (Coordinator.md) and a Swift playground containing the protocol, a concrete FlowCoordinator implementation, and supporting utilities like a Storyboard extension.

Common Design Patterns/Structural/Coordinator · high confidence

Introduced the Delegate structural design pattern, including a Swift implementation with a \DelegateProtocol\ and a \Foo\ class that delegates work to a \Delegate\ conformer, along with a playground and Markdown documentation. Additionally, added the MulticastDelegate pattern, which extends the delegate concept to support multiple delegates via a \MulticastDelegate\<T\>\ class that manages a collection of weakly-referenced delegates, complete with custom operators and playground examples.

Common Design Patterns/Structural/Delegate · high confidence

A new Swift playground demonstrates the Dependency Injection design pattern, featuring a DataStorage class that accepts a Persistence protocol implementation via its initializer. The example includes the Persistence protocol, a Serializable protocol, and two concrete implementations (DataBase and PropertyList) to show how to inject different storage strategies.

Common Design Patterns/Creational/DependencyInjection/DependencyInjection.playground · high confidence

A new Facade design pattern example has been added to the structural patterns section. It demonstrates how to group related APIs (for booking flights and hotels) into a simplified \TravelFacade\ interface, hiding the underlying complexity of the \FlightBooking\ and \HotelBooking\ implementations.

Common Design Patterns/Structural/Facade · high confidence

Introduced the Memento behavioral design pattern, providing a mechanism to save and restore an object's state without breaking encapsulation. The implementation includes a \Memento\ protocol and a \Caretaker\ protocol, with a concrete \PropertyListCaretaker\ that uses \UserDefaults\ for persistence. Example classes \User\ and \Animal\ demonstrate saving and restoring states via state keys, allowing users to revert objects to previous conditions.

Common Design Patterns/Behavioral/Memento · high confidence

A new ObjectPool design pattern has been introduced, providing a thread-safe mechanism for managing a pool of reusable objects. The implementation includes an ObjectPool class that manages a collection of items conforming to the ObjectPoolItem protocol, which defines reuse eligibility and state reset behavior. The pool tracks its state (drained, deflated, full, or undefined) and uses a semaphore to control access, ensuring that objects can be safely enqueued and dequeued. A sample Resource class is included to demonstrate the pattern's usage.

Common Design Patterns/Behavioral/Mediator, Common Design Patterns/Behavioral/Observer/Observer.playground, Common Design Patterns/Creational/ObjectPool/ObjectPool.playground · high confidence

Added a new example of the State behavioral design pattern, implemented as a Swift music player. The change includes a Markdown file explaining the pattern's concepts and a playground file containing the Swift code for the \PlayerContext\ and state structs (\PrepareState\, \PlayState\, \StopState\) that demonstrate how an object changes its behavior when its internal state changes.

Common Design Patterns/Behavioral/State · high confidence

Introduced a new Swift Playgrounds example for the Builder creational pattern. The update adds source files defining a \Burger\ struct and its associated builders (\CheeseBurgerBuilder\, \HamburgerBuilder\) alongside a \BurgerInjectable\ class that uses a closure-based injection approach. The main playground file also includes a modern, keypath-based builder implementation for a \Song\ class, showcasing both classic and dynamic builder styles.

Common Design Patterns/Creational/Builder/Builder.playground · high confidence

A new example for the Abstract Factory creational pattern has been added to the codebase. This includes a Markdown guide (\AbstractFactory.md\) explaining the pattern's purpose and implementation, along with a Swift playground (\AbstractFactory.playground/Contents.swift\) that demonstrates the pattern using vehicle creation logic (e.g., distinguishing between post-apocalyptic and regular cars).

Common Design Patterns/Creational/AbstractFactory · high confidence

Added a new Swift playground and source files demonstrating the Singleton creational design pattern. The update includes three distinct implementations: a standard class-based singleton using a static property, a struct-based singleton using a nested static struct, and a thread-safe singleton using DispatchQueue.once for concurrency control. The accompanying Markdown documentation explains the evolution of Singleton implementations in Swift, from older struct-based workarounds to modern static property approaches, and highlights potential concurrency risks.

Common Design Patterns/Creational/Singleton · high confidence

A new Swift playground has been added to demonstrate the Iterator design pattern. The example defines a Book struct and a Books collection, implementing the IteratorProtocol to allow sequential traversal of the book list. This provides a concrete, runnable example of how to implement the Iterator pattern in Swift.

Common Design Patterns/Behavioral/Command/Command.playground, Common Design Patterns/Behavioral/Iterator/Iterator.playground · high confidence

Added a new entry for the Type Erasure structural design pattern, including a Markdown guide and a Swift playground file. The content explains how to use the pattern to handle protocols with associated types by creating a type-erasing wrapper (e.g., \AnyShelf\) that allows heterogeneous collections of conforming types to be stored in a type-safe manner.

Common Design Patterns/Structural/TypeErasure · high confidence

Introduced the Adapter structural design pattern, which resolves issues with incompatible interfaces by creating an adapter type that wraps an existing type so it can be used by a target interface. The change includes a Markdown guide explaining the three building blocks (Adaptee, Adapter, Target) and a Swift playground example demonstrating a USB-C to Lightning adapter, showing how to implement the pattern using composition to make incompatible protocols work together.

Common Design Patterns/Behavioral/Strategy, Common Design Patterns/Structural/Adapter, Common Design Patterns/Structural/Proxy · high confidence

Introduced a new entry for the Prototype creational design pattern, including a Markdown guide (Prototype.md) that explains the pattern's purpose and usage in Swift, alongside a corresponding Xcode playground (Contents.swift) that demonstrates cloning an AI patrol character to create new instances efficiently.

Common Design Patterns/Creational/Prototype · high confidence

Introduced a new documentation page and a Swift playground example for the Marker structural design pattern. The documentation explains how to use empty protocols to provide run-time metadata to objects, while the accompanying code demonstrates this in a game context, defining \Interactable\, \Destructible\, and \PositionUpdatable\ protocols and corresponding systems to process marked game objects.

Common Design Patterns/Structural/Marker · high confidence

Added new articles and Swift playgrounds for three behavioral design patterns: 'Externalize the Stack' (converting recursive functions to iterative ones using an explicit stack), 'Null Object' (handling nil values with a special-case type), and 'Weak Reference' (preventing memory leaks in the Observer pattern). Each pattern includes a markdown guide and, where applicable, a Swift playground demonstrating the implementation.

Common Design Patterns/Behavioral/Other · high confidence

The Swift Design Patterns library has been expanded with three new pattern entries: the Identifier pattern, which demonstrates type inference and variable binding; the Value-Binding pattern, which covers destructuring enums and tuples; and the Wildcard pattern, which shows how to ignore values. Each pattern is accompanied by a Markdown guide and a corresponding Swift playground file to help users understand and experiment with these language features.

Swift Design Patterns · high confidence

Added documentation and Swift code for three concurrency design patterns. The Balking pattern is introduced as a way to handle method calls when an object is not ready to perform the requested action, preventing blocking in such cases. The Barrier pattern is added to manage access to shared resources using DispatchQueue's barrier flag, ensuring exclusive access for write operations while allowing concurrent reads. The Read-Write Lock pattern is also added, providing a mechanism for multiple threads to read shared data simultaneously while ensuring exclusive write access, implemented using pthread\_rwlock\_t in Swift playgrounds and markdown files.

Concurrency Design Patterns · high confidence

The Xcode project file (project.pbxproj), workspace data, and scheme management files have been deleted from the ios-design-patterns directory. This removes the build configuration and workspace settings for the iOS application and its associated unit and UI test targets.

ios-design-patterns.xcodeproj · high confidence

The default test scaffolding files have been removed from the iOS test targets. Specifically, the \Info.plist\ configuration files and the boilerplate Swift test classes (\ios\_design\_patternsTests.swift\ and \ios\_design\_patternsUITests.swift\) in both the unit and UI test targets have been deleted. This cleanup removes the empty test structures that were previously included by default.

ios-design-patternsTests, ios-design-patternsUITests · high confidence

The default iOS project scaffolding files have been removed from the repository. Specifically, the \AppDelegate\, \ViewController\, \Info.plist\, \LaunchScreen.storyboard\, \Main.storyboard\, and associated asset catalogs have all been deleted. This change strips the project of its standard Xcode-generated entry points and UI definitions, likely as part of a larger refactoring or migration to a different project structure.

ios-design-patterns · high confidence

Written by watchdog.canine.dev from the codebase's own history, inside the signed delivery this page is composed from.

• CAI 43 → 45 (+1.9)
• Rubric changed (rubric-2026.08.18 → rubric-2026.08.19) — scores are not directly comparable.

• Maturity 45 → 52 (+6.6)
• Readiness 24 → 24 (+0.0)
• Security 100 → 100 (+0.0)

• The README contains no architecture or usage description for the Swift design-patterns repository; it is a pure marketing page with no guidance on how to get started or what the patterns do.

Written by watchdog.canine.dev from the codebase's own history, inside the signed delivery this page is composed from.

eleev/swift-design-patterns was measured the same way every project in this corpus was: the same rubric, at a pinned commit, with the result published in full. Point a surveyor at a repository you know and see whether you agree with it.