Swift Academy · Lesson

Creating and Mutating Arrays

Array literals, append, insert, remove and index-based access patterns.

Lesson 1 of 412 steps

Creating and Mutating Arrays is a free Swift Academy lesson on CoddyKit. This is lesson 1 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 4 lessons in total.

Welcome

Arrays are ordered collections of values of the same type. Swift arrays are powerful, safe, and highly optimised. Let's master creation, mutation, and access.

Creating Arrays

```swift let empty: [Int] = [] let nums = [1, 2, 3, 4, 5] var repeated = Array(repeating: 0, count: 5) // [0,0,0,0,0] var range = Array(1...5) // [1,2,3,4,5] ```

Accessing Elements

```swift var fruits = ["apple","banana","cherry"] print(fruits[0]) // apple print(fruits.first!) // apple print(fruits.last!) // cherry print(fruits.count) // 3 ```

append and insert

```swift var arr = [1, 2, 3] arr.append(4) // [1,2,3,4] arr.append(contentsOf: [5,6]) // [1,2,3,4,5,6] arr.insert(0, at: 0) // [0,1,2,3,4,5,6] ```

Removing Elements

```swift var arr = ["a","b","c","d"] arr.remove(at: 1) // ["a","c","d"] arr.removeFirst() // ["c","d"] arr.removeLast() // ["c"] arr.removeAll() // [] ```

Updating Elements

```swift var scores = [80, 90, 70] scores[1] = 95 // [80,95,70] scores[0...1] = [85, 92] // [85,92,70] (range replacement) ```

contains and index(of:)

```swift let nums = [3, 7, 2, 9] print(nums.contains(7)) // true print(nums.firstIndex(of: 2)!) // 2 print(nums.contains { $0 > 8 }) // true ```

isEmpty and capacity

```swift var arr = [Int]() print(arr.isEmpty) // true arr.reserveCapacity(100) // pre-allocate arr.append(contentsOf: 1...100) print(arr.capacity) // >= 100 ```

Combining Arrays

```swift let a = [1, 2, 3] let b = [4, 5, 6] let combined = a + b // [1,2,3,4,5,6] var c = a c += b // [1,2,3,4,5,6] ```

Array Equality

```swift let x = [1, 2, 3] let y = [1, 2, 3] print(x == y) // true — element-wise comparison ``` Arrays are Equatable when their elements are Equatable.

Quick Check

Which method adds an element to the **end** of an array?

Answer it in the interactive lesson

Recap

Key takeaways: • `append`, `insert`, `remove`, `removeAll` — mutation methods • Subscript `arr[i]` for access and update • `+` and `+=` to combine arrays • `contains`, `firstIndex(of:)` for search • `reserveCapacity` for performance when you know the final size Next: sorting, searching, and slicing arrays.

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Frequently Asked Questions

Is the “Creating and Mutating Arrays” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “Creating and Mutating Arrays”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 4 lessons in total.

What will I learn in “Creating and Mutating Arrays”?

Array literals, append, insert, remove and index-based access patterns. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Swift Academy?

No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 4.

How long does the “Creating and Mutating Arrays” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Swift Academy lesson?

Yes. Every Swift Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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