Introduction to Swift

Swift is Apple's language for building iOS, macOS, and watchOS apps — designed to be safe (catching bugs at compile time) and fast (compiling to native machine code).

Optionals (`String?`) explicitly represent 'a value, or nothing' — you must unwrap an optional before using it, which forces you to handle the 'nothing' case rather than crashing at runtime.

Swift favors `let` (a constant) over `var` (a mutable variable) by default — encouraging code where values don't change unexpectedly unless you explicitly opt in.