Swift 5.2 Docs

The Swift Programming Language Documentation v5.2

Swift is a general-purpose programming language built using a modern approach to safety, performance, and software design patterns.

The goal of the Swift project is to create the best available language for uses ranging from systems programming, to mobile and desktop apps, scaling up to cloud services. Most importantly, Swift is designed to make writing and maintaining correct programs easier for the developer. To achieve this goal, we believe that the most obvious way to write Swift code must also be:

Safe. The most obvious way to write code should also behave in a safe manner. Undefined behavior is the enemy of safety, and developer mistakes should be caught before software is in production. Opting for safety sometimes means Swift will feel strict, but we believe that clarity saves time in the long run.

Fast. Swift is intended as a replacement for C-based languages (C, C++, and Objective-C). As such, Swift must be comparable to those languages in performance for most tasks. Performance must also be predictable and consistent, not just fast in short bursts that require clean-up later. There are lots of languages with novel features — being fast is rare.

Expressive. Swift benefits from decades of advancement in computer science to offer syntax that is a joy to use, with modern features developers expect. But Swift is never done. We will monitor language advancements and embrace what works, continually evolving to make Swift even better.

Tools are a critical part of the Swift ecosystem. We strive to integrate well within a developer’s toolset, to build quickly, to present excellent diagnostics, and to enable interactive development experiences. Tools can make programming so much more powerful, like Swift-based playgrounds do in Xcode, or a web-based REPL can when working with Linux server-side code.

Table of Content

About Swift

Version Compatibility

A Swift Tour

The Basics

Basic Operators

Strings and Characters

Collection Types

Control Flow

Functions

Closures

Enumerations

Structures and Classes

Properties

Methods

Subscripts

Inheritance

Initialization

Deinitialization

Optional Chaining

Error Handling

Type Casting

Nested Types

Extensions

Protocols

Generics

Opaque Types

Automatic Reference Counting

Memory Safety

Access Control

Advanced Operators

About the Language Reference

Lexical Structure

Types

Expressions

Statements

Declarations

Attributes

Patterns

Generic Parameters and Arguments

Summary of the Grammar

Document Revision History