SWPatterns.com

Layered Architecture - Kotlin

The Layered Architecture pattern organizes an application into distinct layers, each with a specific role and responsibility. This promotes separation of concerns, making the application more maintainable, testable, and adaptable to change. Common layers include Presentation, Business Logic, and Data Access. My Kotlin …

Snapshot - Kotlin

The Snapshot pattern captures the state of an object at a specific point in time without affecting the original object. This allows for operations like undo/redo, transaction rollback, or simply observing a past state. In this Kotlin example, we use data classes and copy() to create immutable snapshots of a SystemState …

Policy - Kotlin

The Policy pattern allows you to encapsulate a non-functional requirement (like security, logging, or caching) into a separate, reusable component. This avoids scattering such logic throughout your core business logic, promoting separation of concerns and making it easier to modify or extend these policies without …

Specification - Kotlin

The Specification pattern is a behavioral pattern that defines a class for encapsulating business logic in a reusable way. It represents a condition that can be evaluated against an object to determine if it satisfies certain criteria. This promotes decoupling of the logic from the object itself, making the code more …

Null Object - Kotlin

The Null Object pattern replaces null references with objects that have defined, default behavior. This avoids null checks throughout the code, making it more robust and readable. In this Kotlin example, we have a Customer class and a RewardService. Instead of returning null when a customer has no rewards, the …

Visitor - Kotlin

The Visitor pattern allows you to define a new operation without changing 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 input. This is useful when you have a complex object structure and want …

Template Method - Kotlin

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 Kotlin example defines an abstract …

Strategy - Kotlin

The Strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable. It allows an algorithm to vary independently from clients that use it. In this Kotlin example, we use a functional approach with function types to define different shipping strategies (e.g., ground, air). The …

State - Kotlin

The State pattern allows an object to alter its behavior when its internal state changes. It encapsulates each state as a separate class and provides a way to transition between them. This avoids complex conditional logic and makes the code more maintainable and extensible by adding new states without modifying the …

Observer - Kotlin

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. This promotes loose coupling and improved modularity. Here, Subject maintains a list of Observers and notifies them when its data changes. The …