Swift Cheat Sheet

Updated 2026-04-29

Swift is Apple's modern, type-safe programming language for iOS, macOS, watchOS, tvOS, and visionOS development, introduced in 2014 to replace Objective-C. Designed with protocol-oriented programming at its core, Swift combines the performance of compiled languages with the expressiveness of scripting languages while prioritizing safety through features like optionals, strong typing, and Swift 6's compile-time data-race safety. A key mental model: Swift encourages value types (structs) over reference types (classes) for better performance and predictability — think "copy-by-default" rather than "share-by-reference," which fundamentally shapes how you architect Swift applications.

What This Cheat Sheet Covers

This topic spans 26 focused tables and 188 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Type System FundamentalsTable 2: Optionals and UnwrappingTable 3: Control Flow and Pattern MatchingTable 4: Functions and ClosuresTable 5: CollectionsTable 6: Strings and TextTable 7: Property TypesTable 8: GenericsTable 9: Memory Management (ARC)Table 10: Error HandlingTable 11: Concurrency (async/await)Table 12: Protocols and ExtensionsTable 13: Codable / SerializationTable 14: Type Casting and InspectionTable 15: Advanced OperatorsTable 16: Higher-Order FunctionsTable 17: Property WrappersTable 18: SwiftUI Layout ContainersTable 19: SwiftUI NavigationTable 20: InitializationTable 21: Access ControlTable 22: Attributes and AnnotationsTable 23: SubscriptsTable 24: Opaque and Existential TypesTable 25: Swift MacrosTable 26: Swift Testing

Table 1: Type System Fundamentals

Type	Example	Description
struct	`struct Point {` `var x: Int` `var y: Int` `}`	• Value type — copied on assignment or when passed • preferred for most data models.
class	`class Person {` `var name: String` `init(name: String) {` `self.name = name` `}` `}`	• Reference type allocated on the heap — shared when assigned • supports inheritance and deinitializers; use when shared mutable state or identity is needed.
enum	`enum Status {` `case success` `case failure(Error)` `}`	• Value type for a group of related values • supports associated values and raw values; enables exhaustive pattern matching.

Table 1: Type System Fundamentals

Type	Example	Description
struct	`struct Point {` `var x: Int` `var y: Int` `}`	• Value type — copied on assignment or when passed • preferred for most data models.
class	`class Person {` `var name: String` `init(name: String) {` `self.name = name` `}` `}`	• Reference type allocated on the heap — shared when assigned • supports inheritance and deinitializers; use when shared mutable state or identity is needed.
enum	`enum Status {` `case success` `case failure(Error)` `}`	• Value type for a group of related values • supports associated values and raw values; enables exhaustive pattern matching.