For-In Loop

Part of the Fundamentals section of Coddy's Swift journey — lesson 42 of 86.

Loops let you repeat code multiple times without writing it over and over. The for-in loop is Swift's most common loop, perfect for when you know exactly how many times you want to repeat something.

Here's the basic structure:

for number in 1...5 {
    print(number)
}
// Output: 1, 2, 3, 4, 5 (each on a new line)

The loop creates a variable called number that automatically takes each value in the range. The code inside the curly braces runs once for each value. In this case, it runs 5 times.

If you don't need the loop variable, use an underscore to ignore it:

for _ in 1...3 {
    print("Hello!")
}
// Prints "Hello!" three times

The 1...5 is a closed range that includes both 1 and 5. You can also use 1..<5 (half-open range) which includes 1 through 4, but excludes 5.

Challenge

Easy

Read an integer n from input. Use a for-in loop to print all numbers from 1 to n, each on a new line.

You will receive the following input:

A single line containing an integer as a string (e.g., "5")

Read the input, convert it to an Int, and use a for-in loop with a closed range to print each number.

For example, if the input is 4, the output should be:

Cheat sheet

The for-in loop repeats code a specific number of times:

for number in 1...5 {
    print(number)
}
// Output: 1, 2, 3, 4, 5 (each on a new line)

The loop variable (number) automatically takes each value in the range. The code inside the braces runs once for each value.

If you don't need the loop variable, use an underscore:

for _ in 1...3 {
    print("Hello!")
}
// Prints "Hello!" three times

Range operators:

1...5 - closed range (includes both 1 and 5)
1..<5 - half-open range (includes 1 through 4, excludes 5)

Try it yourself

// Read input
let input = readLine()!
let n = Int(input)!

// TODO: Write your code below - use a for-in loop to print numbers from 1 to n

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

The Language Hello World!Comments

4Operators Part 1

Arithmetic Operators Modulo Operator Compound Assignment Recap - Simple Math Comparison Operators

7Basic IO

Print Function String Interpolation ReadLine Input Type Conversion Recap - Till 120 Recap - True or False

10Functions

Declare A Function Parameters And Arguments Return Values Argument Labels Recap - Sigma Function Recap - Validation Function Default Values

13Iterating Over Sequences

Iterating Over Elements The Enumerated Method Iterating Over Strings P1 Iterating Over Strings P2

16Final Challenges

Flat Asterisk Pyramid Pattern Finder What To Buy

2Variables

Let vs Var Type Annotations Numbers String Boolean Naming Conventions Recap - Initialize Variables

5Operators Part 2

Logical Operators Part 1 Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3 Ternary Operator

8Bill Split Calculator

Welcome Message Getting Input

Calculating Tip And Total

Splitting The Bill

Formatted Output

11FizzBuzz with a Twist

Game Overview The FizzBuzz Function

Looping The Numbers

Adding The Twist

14Arrays Advanced

Array Slicing Part 1 Array Slicing Part 2 Sequence Operators The Contains Method