Design patterns are a way of structuring code to make it easy to read, understand and reuse. Kotlin has introduced many new design patterns that you can learn for your next project or overhauling existing projects in the vein of modern coding standards.
It is time to start writing code in Kotlin. This article will take you through the basics of programming, introducing the most valuable design patterns and how they are implemented in this language. We’ll also cover what’s new when it comes to Kotlin with Android Studio 3.2 along with some best practices for testing your application.-Kotlin is a programming language which has become very popular in the Android community. It was released by JetBrains, who you might know for their IntelliJ IDEA IDE. Kotlin helps developers write code more concisely and with fewer errors than other languages on its own platform without needing to learn Java first. This article will talk about some of the design patterns that are possible with Kotlin, including immutable data structures, functional methods, object-oriented principles, and observable sequences.
Kotlin is a statically typed programming language that runs on the Java Virtual Machine. It was designed to be concise and interoperable with Java code. In this blog post, we will explore design patterns in Kotlin.
Patterns in Design
- A design pattern is a generic repeatable solution to a typically recurring issue in software design in software engineering. A design pattern isn’t a finalized design that can be turned into code right away. It’s a description or template for solving an issue that may be applied to a variety of scenarios.
Patterns of design creation
- Singleton
- prototype
- Pool of Objects
- Method of the Factory
- Builder
- Factory of Abstraction
Patterns of structural design
- Adapter
- Bridge
- Composite
- Decorator
- Facade
- Flyweight
- Data from a Private Class
- Proxy
Patterns of behavioral design
- The chain of command
- Command
- Interpreter
- Iterator
- Mediator
- Memento
- Object with no value
- Observer
- State
- Strategy
- technique of a template
- Visitor
Patterns of design creation
Only one object of a given class is ever generated using the singleton technique. All subsequent references to singleton class objects relate to the same underlying instance. There are just a few uses for this design, so don’t abuse it!
UML :
Example:
private constructor of type Counter () count++ companion object val instance = Counter() var count = 0 fun addOne() val instance = Counter() val instance = Counter() val instance = Counter() val instance = Counter() val instance = Counter() val instance = Counter() val instance = Counter() val instance = Counter() val instance
Usage :
Counter = Counter.instance val obj1: val obj2: Counter = Counter.instance obj1.addOne() obj2.addOne() println(“Counter 1: $obj1.count”) println(“Counter 2: $obj2.count”) obj1.addOne() obj2.addOne() obj1.addOne() obj2.addOne() obj1.addOne() obj2.addOne() ob println(“Counter 1: $obj1.count”), println(“Counter 2: $obj2.count”), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one(), one
Output :
Counter number one: two 2nd Counter 1st counter: 2nd Counter: 4
prototype
The cloning operation is delegated to the cloned objects using the Prototype pattern. The rn patte![prototype] specifies a standard interface for all clonable objects. This interface allows you to clone an object without having to tie your code to the object’s class. Typically, such an interface just has one clone method.
In all classes, the clone function is implemented in a similar way. The method produces a new object of the current class with all of the previous object’s field values carried over. Because most programming languages allow objects to access private fields of other objects in the same class, you can even duplicate private fields.
A prototype is an object that allows for cloning. Cloning may be a better option than subclassing when your objects contain dozens of fields and hundreds of potential configurations.
UML :
Example:
Cloneable (ArrayList()) fun add init println(“——-Init——-“) init println(“——-Init——-“) init println(“——-Init——-“) init println images = image(image: String). add(image) println fun showDocument() (“——-Start——-“) “Text: $text”), println(“Text: $text”), println(“Text: $ println println println println print (“Images List: “) images.map println(“Image name: $it”) println(“——-End——-“) println(“——-Begin——-“) println(“——-Begin——-“) println(“——-Begin——- WordDocument? cloneTo() is a lot of fun. As a WordDocument copy, try val copy: WordDocument = super.clone(). This is the text. this.text copy.images = this.text copy.images = this.text copy.images As an ArrayList, images.clone() returns a copy. catch (e: CloneNotSupportedException) return null e.printStackTrace() “> import java.util.ArrayList class WordDocument constructor(var text: String = “”, private var images: ArrayList, ArrayList, ArrayList, ArrayList, ArrayList, ArrayList, ArrayList, ArrayList, ArrayList, Cloneable (ArrayList = ArrayList()) fun add init println(“——-Init——-“) init println(“——-Init——-“) init println(“——-Init——-“) init println images = image(image: String). add(image) println fun showDocument() (“——-Start——-“) images.map println(“Text: $text”) println(“Images List: “) fun cloneTo(): WordDocument? println(“Image name: $it”) println(“——-End——-“) println(“——-Begin——-“) println(“——-Begin——-“) println(“——-Begin——-“) println(“——-Begin- As a WordDocument copy, try val copy: WordDocument = super.clone(). This is the text. this.text copy.images = this.text copy.images = this.text copy.images As an ArrayList, images.clone() returns a copy. take note of (e: CloneNotSupportedException) return null with e.printStackTrace() e.printStackTrace() e.printStackTrace() e.printStackTrace() e.printStackTrace()
Usage :
variable origin fun main() fun main() fun main() fun main() fun main() fun main() fun main WordDocument = WordDocument = WordDocument = WordDocument = WordDocument = WordDocument (). apply addImage text = “This is a paper” (“Image 1”) includeAnImage (“Image 2”) includeAnImage (“Image 3”) showDocument() is a function that displays a document. copy of val Doc: WordDocument? = originDoc.cloneTo()?.apply Doc: WordDocument? = originDoc.cloneTo()?.apply addImage(“A new image”) showDocument() text = “This is a copy document” showDocument() !!copyDoc!!.showDocument()!!copyDoc!!.showDocument()!!copyDoc!!.
Output:
———————————————————————————————————— Start ——- Images List: This is a document Text: This is a document Image 1: Image 2: Image 3: Image 4: Image 5: Image 6: Image 7: Image 8: Image 9: Image 10: Image 11: Image 12: Image ——-End ——- ———— Start ——- Images List: This is a document Text: This is a document Image 1: Image 2: Image 3: Image 4: Image 5: Image 6: Image 7: Image 8: Image 9: Image number three ——-End ——- ———— Start ——- Text: This is a scanned copy of a document. Images: Image 1: Image 2: Image 3: Image 4: Image 5: Image 6: Image 7: Image 8: Image 9: Image 10: Image 11: Image 12: Image A new picture has been created. ——-End ——- ———— Start ——- Text: This is a scanned copy of a document. Images: Image 1: Image 2: Image 3: Image 4: Image 5: Image 6: Image 7: Image 8: Image 9: Image 10: Image 11: Image 12: Image A new picture has been created. ——-End ——-
Builder
The builder pattern is used to design complicated structures having component elements that must be assembled in a precise sequence or according to a set of rules. The construction algorithm is controlled by an external class.
UML :
Example:
data type constructor for a car (var color: String, var license: String) private constructor(builder: Builder): this (plate: String, var brand: String) ( builder.color, builder.licensePlate, builder.brand ) lateinit var color: String lateinit var licensePlate: String lateinit var brand: String lateinit var color: String apply fun color(init: Builder.() -> String) color = init(); color = init(); color = init(); color = init(); color a good time license apply Plate(init: Builder.() -> String) licensePlate = init(); licensePlate = init(); licensePlate = init(); licensePlate = in companion object fun build(init: Builder.() -> Unit) = Car(Builder().apply(init)) fun brand(init: Builder.() -> String) = apply brand = init()
Usage:
val car1 = Car.build val car1 = Car.build val car1 = Car.build val car1 = Car.build val car1 = Car.build val car1 = Car.build val car1 = Car.build val car1 = Car.build val car1 = Car. println(car1)
Output:
Automobile (color=blue, licensePlate=C88888, manufacturer=Audi)
Method of the Factory
The factory pattern replaces class constructors by abstracting the object creation process so that the type of the object created may be specified at runtime.
UML :
Example:
Cake is a lot of fun to make. Materials(); enjoyable banking();
override fun prepareMaterials() println(“prepare Mango Cream”) println(“prepare Mango Cream”) println(“prepare Mango Cream”) println(“prepare Mango Cream”) println(“prepare Mango Cream”) println(“prepare Man println(“Baking 10 minutes”) override fun banking()
createProduct(clz:Class): T? abstract class Factory abstract fun createProduct(clz:Class): T?
override fun CakeFactory: Factory() class T? createProduct(clz: Class) var cake: Cake? = null var cake: Cake? = null var cake: Cake? = null var try cake = Class.forName;;;;;;;;;;;;;;;;; (clz.name). getDeclaredConstructor(). Cake as newInstance() take note of (e : Exception) Return cake as T with e.printStackTrace()?
Usage :
Factory = CakeFactory is a val factory () val mangoCake = factory.createProduct(MangoCake::class.java)?.apply prepareMaterials() banking() val mangoCake = factory.createProduct(MangoCake::class.java)?.apply val mangoCake = factory.createProduct(MangoCake::class.java
Outpu:
fifteen minutes to make Mango Cream Baking
Factory of Abstraction
The abstract factory pattern is used to provide a group of linked or dependent objects to a customer. The factory’s “families” of items are determined at run-time.
UML :
Example:
CakeFactory is an abstract class. abstract fun cream():CakeCream is an abstract fun style():CakeStyle is an abstract fun style():CakeStyle is an abstract fun style():CakeStyle is an abstract fun style():CakeStyle is an abstract fun
CakeCream is an abstract class, and cream() is an abstract fun function.
CakeStyle is an abstract class with an abstract fun style() method.
override fun style() println(“Heart Style”) class HeartStyle:CakeStyle()
override fun cream() println(“Mango Cream”) class MangoCream:CakeCream()
override fun cream(): CakeCream class MangoHeartCake: CakeFactory() class MangoHeartCake: CakeFactory() class MangoHeartCake: CakeFactory() class MangoHeart if MangoCream() is true, return MangoCream(); if MangoCream() is false return HeartStyle() override fun style(): CakeStyle
Usage :
var mangoHeartCake: CakeFactory = MangoHeartCake() mangoHeartCake.cream().cream() mangoHeartCake.style().style() mangoHeartCake.style().style() mangoHeartCake.style().style() mangoHeartCake.style().style() mangoHeartCake.style().style() mangoHeartC () println(“=================”) var mangoSquareCake: CakeFactory = MangoSquareCake() mangoSquareCake.cream().cream() mangoSquareCake.style().style() mangoSquareCake.style().style() mangoSquareCake.style().style() mangoSquareCake.style().style() mangoSquareCake.style().style() mangoSquare ()
Outpu:
Mango Cream Square Style ========================================================
Patterns of Structure:
Proxy for Security
The proxy pattern is used to create a placeholder or surrogate object that refers to an underlying object. Access is being restricted by a protection proxy.
UML :
Example:
fun receiveMessage() fun takeCourier() fun signatureAcceptance() interface IPicker
RealPicker:IPicker is a class that represents a picker. println(“Receive text Message”) override fun receiveMessage() println(“Take the Courier”) override fun takeCourier() override signatureAcceptance() println(“Signature Acceptance”) println(“Signature Acceptance”) println(“Signature Acceptance”) println(“Signature Acceptance”) println(“Signature Acceptance
IPicker by picker, class ProxyPicker(private val picker: IPicker): IPicker by picker, class ProxyPicker(private val picker: IPicker): IPicker by pick
Usage :
IPicker = RealPicker val picker:IPicker val picker:IPicker val picker:IPicker () proxyPicker = ProxyPicker(picker) proxyPicker; val proxyPicker = ProxyPicker(picker) proxyPicker; val proxyPicker = Proxy proxyPicker.receiveMessage() proxyPicker takeCourier() signatureAcceptance()
Outpu:
Text Messages Received Accept the Signature Acceptance from the Courier
Decorator
The decorator pattern is used to wrap objects in an object of a decorator class to extend or change their functionality at runtime. This is a more versatile option than utilizing inheritance to change behavior.
UML :
Example:
Cake fun make() interface
override fun create() println(“Baking Cake”) class CakeEmbryo: Cake
a free class Cake by cake, constructor DecoratorCake(val cake: Cake):
override fun make() addSomeFruit() super.make() class FruitCake constructor(cake:Cake):DecoratorCake(cake) println(“Add Some Fruit”) private fun addSomeFruit()
Usage :
Cake = Cake, val cake, val cake, val cake, val cake, cake.make() Embryo() Embryo() Embryo() Embryo() Embryo() Emb (“————Decorate Fruit Cake————”) var fruitCake: FruitCake = DecoratorCake (cake) fruitCake.make()
Outpu:
——————————————————————————— ————————————————————————————————— Adding Fruit to the Baking Cake
Adapter
The adapter pattern is used to create a connection between two types that are otherwise incompatible by wrapping the “adaptee” in a class that supports the client’s interface.
UML :
Example:
fun provideVoltFive():Int interface VoltFive interface VoltFive interface VoltFive interface VoltFive interface VoltFive interface VoltFive interface VoltFive
Volt220 is a great class to offer. Int return 220; Volt220(); Volt220(); Volt220(); Volt220(); Volt220(); Volt220()
VoltFive override fun supply class VoltAdapter(private val volt220: Volt220): Int val volt = volt220.provideVolt220() return 5 VoltFive(): Int val volt = volt220.provideVolt220() return 5 offer amusement return volt220.provideVolt220() volt220() volt220() volt220() volt220() volt220() volt220() volt220() volt220() volt220() volt
Usage :
Volt220 = val volt220 () val adapter is the same as VoltAdapter (volt220) println(“After adapter, the volt is: $volt”) val volt = adapter.provideVoltFive()
Outpu:
The voltage is 5 volts after the adaptor.
Facade
The facade design is used to provide a more simple interface to a more complicated subsystem.
UML :
Example:
fun lasagneWithTomatoAndCheese() fun prawnRisotto() fun creamCaramel() interface Italykitchen
ItalykitchenImpl class: Italykitchen println(“Lasagne With Tomato And Cheese”) println(“Lasagne With Tomato And Cheese”) println(“Lasagne With Tomato And Cheese”) println(“Lasagne With Tomato And Cheese”) println(“Lasagne With Tomato And Cheese”) println(“Lasagne With Tomato println(“Prawn Risotto”) override fun prawnRisotto() println(“Cream Caramel”) override fun creamCaramel()
bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse()
FrenchkitchenImpl is a class that represents a French kitchen. bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() println(“Cassoulet”) override fun cassoulet() println(“PouleAuPot”) override fun pouleAuPot()
Italykitchen: Italykitchen: Italykitchen: Italykitchen: Italykitchen: Italykitchen: Italykitchen: Italykitchen: Italykitchen: Italykitchen a private room italykitchen = ItalykitchenImpl() frenchkitchen = FrenchkitchenImpl() init italykitchen = ItalykitchenImpl() init italykitchen = ItalykitchenImpl() init italykitchen = ItalykitchenImpl() init italykitchen = ItalykitchenI bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse() bouillabaisse cassoulet() is a fun function in the frenchkitchen.cassoulet() package. frenchkitchen.pouleAuPot() is a fun pouleAuPot() method. italykitchen.lasagneWithTomatoAndCheese() italykitchen.lasagneWithTomatoAndCheese() italykitchen.lasagneWithTomatoAndCheese() italykitchen.lasagneWithTomatoAndCheese() italykitchen italykitchen.prawnRisotto() prawnRisotto() prawnRisotto() prawnRisotto() prawnRisotto() prawnRisotto() pra italykitchen.creamCaramel() a fun creamCaramel() a fun creamCaramel() a fun creamCaramel() a fun creamCaramel() a fun creamCaramel() a
Usage :
menu is a variable () menu.lasagneWithTomatoAndCheese() menu.cream() println(“Customer order”) println( Caramel() “New Order =============================== println(“Customer two orders” ===================================== “(menu) menu.prawn bouillabaisse() Risotto()
Outpu:
Customer requests Lasagne with Cream Caramelized Tomatoes and Cheese. New Order=================================================== Customers placed two orders. Risotto de prawns de Bouillabaisse
GitHub
Visit Github for further information.
The “android design patterns pdf” is a book that discusses the history, definition, and implementation of design patterns. The book was written by Robert C. Martin.
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Frequently Asked Questions
What are kotlin design patterns?
A: Kotlin is an object-oriented, statically typed programming language that runs on the Java Virtual Machine. It was designed by JetBrains in order to better cope with large codebases and modern multi-platform software development.
Should you use builder pattern in Kotlin?
A: It is recommended to use builder pattern in Kotlin.
What is the best design pattern in Android?
A: The MVC design pattern is the most common and accepted design pattern in Android. It stands for Model-View-Controller, which describes a software architecture that separates the data from how its presented to users by placing them into different layers of abstraction, all with its own responsibilities and interaction between each other.
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