Array Slicing Part 1

Part of the Fundamentals section of Coddy's Swift journey — lesson 73 of 86.

Sometimes you don't need an entire array—just a portion of it. Swift makes it easy to extract a subset of elements using array slicing with range operators.

To get a slice, you use a range inside the subscript brackets. The most common approach uses the half-open range operator (..<), which includes the start index but excludes the end index:

let numbers = [10, 20, 30, 40, 50]
let slice = numbers[1..<4]
print(slice)  // [20, 30, 40]

Here, 1..<4 gives us elements at indices 1, 2, and 3—but not index 4. This is useful when you know exactly where you want to stop.

If you want to include the end index, use the closed range operator (...):

let letters = ["a", "b", "c", "d", "e"]
let slice = letters[1...3]
print(slice)  // ["b", "c", "d"]

One important detail: the result of slicing is an ArraySlice, not a regular Array. If you need a true array, wrap it with Array():

let original = [1, 2, 3, 4, 5]
let sliced = Array(original[0..<3])
print(sliced)  // [1, 2, 3]

Challenge

Easy

Write a function getMiddleElements that takes numbers, start, and end and returns a slice of the array from the start index up to (but not including) the end index.

Use the half-open range operator (..<) to extract the specified portion of the array and return it as a regular array.

Parameters:

numbers ([Int]): The array to slice
start (Int): The starting index (inclusive)
end (Int): The ending index (exclusive)

Returns: An array containing elements from the start index up to (but not including) the end index ([Int])

Example: If numbers is [10, 20, 30, 40, 50, 60], start is 1, and end is 4, the function should return [20, 30, 40].

Cheat sheet

Swift allows you to extract a portion of an array using array slicing with range operators.

Use the half-open range operator (..<) to slice from a start index up to (but not including) an end index:

let numbers = [10, 20, 30, 40, 50]
let slice = numbers[1..<4]
print(slice)  // [20, 30, 40]

Use the closed range operator (...) to include the end index:

let letters = ["a", "b", "c", "d", "e"]
let slice = letters[1...3]
print(slice)  // ["b", "c", "d"]

Array slicing returns an ArraySlice. To convert it to a regular Array, wrap it with Array():

let original = [1, 2, 3, 4, 5]
let sliced = Array(original[0..<3])
print(sliced)  // [1, 2, 3]

Try it yourself

func getMiddleElements(numbers: [Int], start: Int, end: Int) -> [Int] {
    // Write code here
}

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 1Array Slicing Part 2 Sequence Operators The Contains Method