Language basics

27 steps in 9 sets of Swift.

Swift is Apple's 2014 answer to a question Objective-C had carried for thirty years: what would the platform language look like designed fresh? The answer — value types first, optionals instead of nil crashes, protocols over inheritance, closures everywhere — became the language of iOS and macOS development, then grew a serious life on Linux servers and in the Vapor and AWS Lambda worlds. It compiles through LLVM to fast native code and reads closer to a scripting language than its performance suggests.

This tour types the core: let and var, interpolation, guard and the pattern-matching switch, ranges and stride, argument labels, trailing closures with $0, the map/filter/reduce trio, the whole optional toolkit from ?? to guard let to chaining, the value-type collections, structs against classes, computed properties, protocols with extensions, enums with associated values, generics, and errors from throws through Result to defer. The Encore is the cross-language script trio in modern Swift — defaulted subscripts, range patterns, and zip.

Start this tour

Values

The program shapeThe smallest Swift: top-level code, print, interpolation.
let and varConstants by default, mutation by request, types by inference.
String interpolationBackslash-parens splice values; triple quotes span lines.

Control flow

if and guardguard bails early so the happy path stays unindented.
switch patternsExhaustive matching over ranges, wheres, and tuples.
Ranges and loops1...3 includes the end, 0..<3 stops short, stride steps.

Functions & closures

Argument labelsCall sites read like prose; underscores opt out.
ClosuresTrailing braces and $0: the shape of everyday Swift.
map, filter, reduceThe functional trio, plus compactMap for the misses.

Optionals

OptionalsThe maybe-missing value, spelled into the type.
if let and guard letUnwrap by shadowing: same name, non-optional inside.
Optional chainingOne ? short-circuits the whole path to nil.

Collections

Arrays and dictionariesValue-type collections with literal syntax.
enumerated and zipWalk with indices, or walk two sequences in lockstep.
SetsDeduplication plus algebra: union, intersection, subtracting.

Structs & classes

Structs are valuesAssignment copies; writers say mutating.
Classes are referencesTwo names, one object; === asks about identity.
Computed propertiesDerived on read, observed on write.

Abstractions

Protocols and extensionsState the requirement; share the implementation.
Associated valuesEnum cases carry payloads; switch unpacks them.
GenericsType parameters at the call site, bounded where needed.

Errors & scope

ErrorsTyped throws routed by do, try, and catch.
ResultSuccess or failure as a value, switched like any enum.
deferCleanup scheduled at entry, run at every exit.

Encore

word_freq.swiftA word-frequency table from split, a defaulted subscript, one sort.
grade_report.swiftReport cards from a struct roster, range patterns, and format.
temp_stats.swiftA week of temperatures: min/max by closure, a bar chart, zip swings.