Swift Concepts: Opaque Types & Existential Types

This article delves into the theory and practice of using anyand some, elucidating their roles, differences, and practical applications in app development.

Swift Concepts: Opaque Types & Existential Types

Introduction

Swift, the powerful and intuitive programming language for macOS, iOS, watchOS, and tvOS app development, continues to evolve. With the introduction of Swift 5.1, two new keywords, any and some, have been added to handle types more effectively: opaque types and existential types. Understanding these keywords is essential for both beginner and expert developers to write efficient and robust Swift code.

Theory

Explanation for Beginners

Opaque Types (some)

Opaque types, introduced with the some keyword, allow you to specify a type without revealing its exact type. This can be particularly useful when you want to abstract the details of the return type while ensuring it conforms to a protocol.

Example:

func makeShape() -> some Shape {
    return Circle()
}

Here, makeShape returns a type that conforms to the Shape protocol, but the exact type is hidden (opaque).

Existential Types (any)