0x30Lesson 4 of 7

Decide with conditions

Use `if`, comparisons, and booleans to branch.

15 min 5-question quiz 1 code exercise

By the end of this lesson you can

Write clear if/else logic from input values.

Swift conditions evaluate to Bool. Use if, else if, and else to choose behavior. Comparison operators include ==, !=, <, <=, >, and >=; combine conditions with && and ||.

main.swift

1let score = 82
2if score >= 90 {
3    print("A")
4} else if score >= 80 {
5    print("B")
6} else {
7    print("Keep practicing")
8}

Output

Swift also includes guard for early exits, which can simplify control flow in functions by handling invalid cases first.

Key takeaways

Write clear if/else logic from input values.
Swift favors clear intent and safe defaults.
Compiler feedback is part of the learning loop.

Lesson quiz

5 questions · pass with 4 correct · up to 50 XP

Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.

Practice: write Swift

These run for real. Write the program, press Run tests, and read what the compiler tells you - learning to read compiler messages is half of learning C.

Exercise 1

Label a temperature

+25 XP

Read one integer and print cold if below 15, otherwise print warm.

Below threshold
At threshold

main.swift

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Swift lessons are authored for Swift 6.4; exercises run on Swift 6.0.1 via Wandbox, a free public service. Your source code and test input are sent to that service.

Questions about this lesson

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