Design Patterns in Kotlin

As Kotlin continues to gain popularity in modern software development, especially in Android development, understanding design patterns becomes increasingly vital. These patterns, deeply entrenched in the history of object-oriented programming, provide proven solutions to common problems. Kotlin, with its expressive syntax and powerful features, makes implementing these patterns more intuitive and concise.


Design patterns are typical solutions to common problems in software design. They're like tried-and-tested templates that, once recognized, can be utilized to address frequent design issues in object-oriented software development.


Design patterns are mainly grouped into three categories: Creational, Structural, and Behavioral. 

1. Creational Patterns: 

Concerned with the process of object creation. 

Singleton Design Pattern

Ensures that a class has just one instance and provides a way to access it. In Kotlin, you can easily create a singleton using the object keyword.

Tutorial: Singleton Design Pattern in Kotlin

Factory Method Design Pattern

Defines an interface for creating an instance, but lets subclasses decide which class to instantiate. With Kotlin's powerful type system and first-class functions, factories can be more expressive. 

Tutorial: Factory Method Design Pattern in Kotlin

Abstract Factory Design Pattern

Offers an interface for creating families of related or dependent objects without specifying their concrete classes. 

Tutorial: Abstract Factory Design Pattern in Kotlin

Builder Design Pattern

Allows for the creation of complex objects step by step. Kotlin's named and default arguments can simplify the builder pattern implementation. 

Tutorial: Builder Design Pattern in Kotlin

Prototype Design Pattern

Allows for copying an existing object instead of creating a new instance from scratch. 

Tutorial: Prototype Design Pattern in Kotlin

2. Structural Patterns: 

Concerned with how classes and objects can be composed, to form larger structures. 

Adapter Design Pattern

Allows objects with incompatible interfaces to work together. Kotlin's extension functions can be incredibly useful here. 

Tutorial: Adapter Design Pattern in Kotlin

Bridge Design Pattern

Decouples an abstraction from its implementation, allowing both to vary independently. 

Tutorial: Bridge Design Pattern in Kotlin

Composite Design Pattern

Allows clients to treat individual objects and compositions uniformly. 

Tutorial: Composite Design Pattern in Kotlin

Decorator Design Pattern

Adds responsibilities to an object dynamically. With Kotlin, you can utilize extension functions or delegation.

Tutorial: Decorator Design Pattern in Kotlin

Facade Design Pattern

Offers a simplified interface to a larger body of code, such as a library. 

Tutorial: Facade Design Pattern in Kotlin

Flyweight Design Pattern

Shares objects to support large quantities of fine-grained objects efficiently. 

Tutorial: Flyweight Design Pattern in Kotlin

Proxy Design Pattern

Provides a surrogate or placeholder for another object. 

Tutorial: Proxy Design Pattern in Kotlin

3. Behavioral Patterns: 

Focus on communication between objects, how objects operate, and their responsibilities. 

Chain of Responsibility Design Pattern

Passes requests along a chain of potential handlers until an object handles them. 

Tutorial: Chain of Responsibility Design Pattern in Kotlin.

Command Design Pattern

Converts operations into stand-alone objects that contain information about the operation. 

Tutorial: Command Design Pattern in Kotlin.

Interpreter Design Pattern

Implements a specialized language's grammar. 

Tutorial: Interpreter Design Pattern in Kotlin.

Iterator Design Pattern

Provides a way to access elements of an aggregate object sequentially without exposing its underlying representation. In Kotlin, this is heavily used in for loops with iterable objects. 

Tutorial: Iterator Design Pattern in Kotlin.

Mediator Design Pattern

Reduces coupling between classes by offloading their communications. 

Tutorial: Mediator Design Pattern in Kotlin.

Memento Design Pattern

Captures and restores an object's internal state. 

Tutorial: Memento Design Pattern in Kotlin.

Observer Design Pattern

Lets objects notify each other of changes without specifying who is notified. Kotlin's Observable can be handy here. 

Tutorial: Observer Design Pattern in Kotlin.

State Design Pattern

Allows an object to change its behavior when its internal state changes. 

Tutorial: State Design Pattern in Kotlin.

Strategy Design Pattern

Defines a set of encapsulated algorithms that can be swapped to carry out a specific behavior. 

Tutorial: Strategy Design Pattern in Kotlin.

Template Method Design Pattern

Defines the program skeleton in an algorithm in an algorithmic method. 

Tutorial: Template Method Design Pattern in Kotlin

Visitor Design Pattern

Adds further operations to objects without having to modify them. 

Tutorial: Visitor Design Pattern in Kotlin