Repeat work with loops and collections
Use loops and arrays to process many values.
- Iterate through collections and accumulate results.
Swift arrays hold ordered values. Use for value in values to iterate cleanly, or use ranges like 0..<count when you need indexes. Build running totals with mutable variables and keep loop bodies simple.
1let scores = [8, 7, 10]
2var total = 0
3for score in scores {
4 total += score
5}
6print(total)25
..< is a half-open range that includes the start and excludes the end. This is ideal for zero-based indexing because 0..<array.count stays in bounds.
Key takeaways
Iterate through collections and accumulate results.
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.
Sum N numbers
Read a count, then read that many integers (one per line), and print their sum.
- Three numbers
- Negative number
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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