Control Flow

By the end of this lesson you'll make decisions with if / else , wield Swift's exhaustive switch with ranges and pattern matching, repeat work with for-in , while and repeat-while , and safely unwrap optionals with guard let and if let — the logic skeleton of every real Swift program.

Learn Control Flow in our free Swift course — a beginner-friendly interactive lesson with worked examples, a practice exercise and a quick reference.

Part of the free Swift course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

What You'll Learn in This Lesson

1️⃣ Conditionals: if / else

A conditional runs code only when a test is true. The test must be a Bool — a true/false value — which you build with comparisons like , , == (equal) and != (not equal), and combine with && , || , and ! . Read this worked example and run it, then you'll write your own.

Your turn. The program below is almost finished — fill in the blanks marked ___ using the // 👉 hints, then run it and check the expected output.

2️⃣ Swift's Powerful switch

Swift's switch is in a different league from C or Java. Two rules shape everything: it must be exhaustive (cover every possible value — usually via a default: case), and there is no implicit fall-through (only the matching case runs, so you never write break ). On top of that you can match ranges ( 90...100 ), match and destructure tuples , bind matched values with let , and add extra conditions with where .

Now you finish a grade classifier. Fill in the missing range and the catch-all keyword:

3️⃣ Loops: for-in, while & repeat-while

Loops repeat work. for-in walks through a sequence — a range like 1...5 or an array. while repeats while a condition holds, checking before each pass (so it can run zero times). repeat-while checks after , so its body always runs at least once. A range with ... includes its end; with ..< it stops just before it.

4️⃣ Optionals: guard let & if let

An optional is a value that might be missing — its type ends in ? , and "missing" is written nil . You can't use an optional directly; you must unwrap it. if let (optional binding) runs a block only when a value is present. guard let is the early-exit twin: if the value is missing it forces you to leave the scope right away, and otherwise the unwrapped value stays available for the rest of the function — keeping your main logic flat instead of buried in nested if s.

📋 Quick Reference — Control Flow

No blanks this time — just a brief and an outline. Write it yourself, run it, and check your output against the expected lines in the comments. FizzBuzz combines a loop, the remainder operator, and an if/else chain — exactly this lesson's toolkit.

Practice quiz

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