Kotlin Sealed Class: Exploring Powerful Abstractions

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Kotlin Sealed Class: Exploring Powerful Abstractions

The sealed class is a unique and forced construct that lets creators designate bounded class pecking orders with a bounded bunch of subclasses. It brings additional control and flexibility to the class-based paradigm, enabling the creation of strong and expressive code. We’ll go through the concept of sealed classes in detail, including their objective, use, and privileges. 

Kotlin Sealed Class: Exploring Powerful Abstractions

by

Viktoriia Domukhovska

August 5, 2023

The kotlin sealed class is a unique and forced construct that lets creators designate bounded class pecking orders with a bounded bunch of subclasses. It brings additional control and flexibility to the class-based paradigm, enabling the creation of strong and expressive code. We’ll go through the concept of sealed classes in detail, including their objective, use, and privileges. 

Concertation on Sealed Classes

1. The Kotlin Sealed Class Overview:

• Utilizing the sealed modifier defines a sealed class, which restricts the class’s descent to finite subclasses designated within the same file.
• People commonly utilize sealed classes to present bounded kinds, such as an original bunch of info states or alternative outcomes of an operation.

2. Privileges of Sealed Classes:

• Enhanced kind Security: Sealed classes help eliminate runtime mistakes by defining a closed bunch of subclasses, ensuring comprehensive handling of all feasible cases.
• Enhanced Abstraction: Sealed classes let a concise way to present complex state-based logic, promoting clean and self-contained code.
• Template Matching: Kotlin’s sealed classes make it less difficult to employ template matching, enabling creators to promote numerous subclasses and run particular code blocks based on the sealed class instance.

3. Diversities Between Sealed Class and Other Modifiers:

• Final vs sealed: While last bounds up further subclassing, sealed lets a bounded count of subclasses. Viewers could perceive sealed classes as a fixed version of abstract classes.
• Internal vs sealed: The internal modifier regulates the visibility of a declaration within a module, while the sealed modifier controls the ranking and restricts the count of possible subclasses for a sealed class.

Utilizing Sealed Classes

See a scenario of modeling kinds of literature. It is the subclass of the head-sealed class ‘Literature.’ ‘Scientific’ and ‘Fiction’ are subclasses inherited from ‘Literature’ and override the ‘getNumberOfPages’ method.

sealed class Literature {
    abstract fun getNumberOfPages()
}

class Scientific: Literature() {
    override fun getNumberOfPages() {
        println("Scientific contains 200 pages")
    }
}
class Fiction: Literature() {
    override fun getNumberOfPages() {
        println("Fiction contains 100 pages")
    }
}
fun getPageByTypeOfBook(literature: Literature) {
    when(literature) {
        is Fiction - > literature.getNumberOfPages()
        is Scientific - > literature.getNumberOfPages()
    }
}
fun main() {
    val scientific = Scientific()
    val fiction = Fiction()
    getPageByTypeOfBook(scientific) // Output: Scientific contains 200 pages
    getPageByTypeOfBook(fiction) // Output: Fiction contains 100 pages
}

Sealed Interfaces in Kotlin

The kotlin sealed class restricts access similarly to a sealed interface. It differs from a sealed class in that it lacks state and behavior. The system uses sealed interfaces to establish a constrained type range for interface implementation. You must declare all sealed interface implementations in the same file as the sealed interface. 

sealed interface Literature {
    class Fiction(val page: Int): Literature
    class Scientific(val page: Int, val color: String): Literature
}