swift-pattern-matching-case-let.md

title	pattern matching with case let in Swift
date	2019-02-08
captured	2019-02-08 16:24:25 UTC
tags	swift pattern-matching syntax
source	GitHub issue #409 + https://swiftwithmajid.com/2019/02/06/pattern-matching-with-case-let/
aliases
status	refined

Context

Swift's case let keyword enables powerful pattern matching across enums, optionals, and tuples. This provides elegant, readable syntax for destructuring and filtering complex data types.

Source: Pattern Matching with case let

Enums with associated values

Extract associated values from enum cases with optional filtering:

case let .loaded(shows)                           // extract value
case let .loaded(shows) where shows.isEmpty       // extract + condition

Optionals

Since optionals are enums (Optional<T>), pattern matching applies directly:

case let value?    // matches non-nil (equivalent to .some(value))
case .none         // handles nil

Tuples

Pattern matching works with tuple grouping:

case ("admin", "admin")                                    // match specific values
case let (_, password) where password.count < 6            // wildcard + condition

Control flow integration

case let integrates with multiple Swift constructs:

• if case let - conditional checks with extraction
• guard case let - early returns when pattern does not match
• for case let - loop filtering: for case let .loaded(shows) in collection where condition

Key takeaway

Pattern matching with case let reduces boilerplate while improving code clarity. It replaces verbose switch statements and nested if let chains with concise, expressive syntax that works consistently across enums, optionals, and tuples.

Related

• [[swifty-code]] - broader principles for idiomatic Swift