Swift Academy · Lesson

Replacing and Splitting Text

Transform strings using regex operations.

Lesson 4 of 413 steps

Replacing and Splitting Text is a free Swift Academy lesson on CoddyKit. This is lesson 4 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.

Replacing and Splitting

Regex is not only for matching. Swift strings can replace matched text and split on a pattern, transforming strings without manual loops.

replacing(_:with:)

replacing(_:with:) returns a new string where every match of the pattern is swapped for the replacement text.

let s = "a1b2c3"
let cleaned = s.replacing(/\d/, with: "*")
print(cleaned)

Replacing Whole Words

The pattern can be any regex, so you can replace all runs of digits at once with a single replacement.

let s = "order 1234 done"
let masked = s.replacing(/\d+/, with: "#")
print(masked)

Mutating with replace

replace(_:with:) modifies a var string in place rather than returning a copy.

var text = "hello world"
text.replace(/o/, with: "0")
print(text)

Replacing with a Closure

The replacing(_:with:) closure form receives each match and returns the replacement, enabling computed substitutions.

let s = "a1 b2 c3"
let result = s.replacing(/\d+/) { match in
    String((Int(match.0) ?? 0) * 10)
}
print(result)

Using Captures in Replacement

Inside the closure you can read capture groups from the match to build the replacement text.

let s = "2024-05"
let out = s.replacing(/(\d+)-(\d+)/) { m in
    "\(m.2)/\(m.1)"
}
print(out)

split(separator:)

Strings support split(separator:) with a regex, breaking the string wherever the pattern matches.

let csv = "a,b;c,d"
let parts = csv.split(separator: /[,;]/)
print(parts)

Splitting on Whitespace

A common task: split a string into words on any run of whitespace using /\s+/.

let line = "the   quick  brown"
let words = line.split(separator: /\s+/)
print(words.count)
print(words)

Limiting Splits

The maxSplits parameter caps how many splits occur, keeping the remainder intact.

let s = "a-b-c-d"
let parts = s.split(separator: /-/, maxSplits: 1)
print(parts)

Trimming and Replacing

Combine operations: replace unwanted patterns, then split, to clean and tokenize input in a pipeline.

let raw = "  one,, two ,,three "
let cleaned = raw.replacing(/,+/, with: ",")
let items = cleaned.split(separator: ",").map { $0.trimmingCharacters(in: .whitespaces) }
print(items)

replacing vs replacingOccurrences

The regex replacing works on patterns; the older replacingOccurrences(of:with:) only handles literal substrings. Prefer the regex form for pattern-based edits.

let s = "cat hat bat"
print(s.replacing(/[ch]at/, with: "X"))

Quick Check

What does "a1b2".replacing(/\d/, with: "-") produce?

Answer it in the interactive lesson

Recap

You can replace matches with replacing(_:with:) (string or closure form) and the in-place replace, and split strings on a regex with split(separator:) plus maxSplits. These turn regex into a full text-transformation toolkit.

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Frequently Asked Questions

Is the “Replacing and Splitting Text” lesson free?

Yes — any 3 lessons of the Swift Academy learning path, including “Replacing and Splitting Text”, 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 “Replacing and Splitting Text”?

Transform strings using regex operations. 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 4 of 4.

How long does the “Replacing and Splitting Text” 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?

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