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Strings

By · Reviewed & last updated · Part of Swift Tutorial

Swift strings are Unicode-correct: they iterate by extended grapheme clusters, not bytes or code units. The price is no O(1) indexing — positions use String.Index.

The strings API you actually use

EXAMPLE
let name = "Ada Lovelace"
print(name.count)            // 12 (visible characters)
print(name.uppercased())
print(name.split(separator: " "))   // ["Ada", "Lovelace"]

// Interpolation
let age = 36
let greeting = "Hi, \(name)! You are \(age)."

// Multi-line literal
let body = """
    Dear \(name),
      Welcome to Swift.
    --
    Team
    """

// Mutating
var s = "Hello"
s.append(", world")
s += "!"

// Indices — NOT Int. Use String.Index.
let first = name[name.startIndex]                       // 'A'
let four  = name.index(name.startIndex, offsetBy: 4)
let rest  = name[four...]                               // "ovelace"

// Find / replace
if let r = name.range(of: "Lovelace") {
    print(name[r])
}
let patched = name.replacingOccurrences(of: "Lovelace", with: "the Countess of Lovelace")

// Iterate as Characters / Unicode / UTF-8
for ch in name { print(ch) }                            // grapheme clusters
name.unicodeScalars.forEach { print(\$0.value) }
name.utf8.forEach { print(\$0) }

Why it matters

String length isn’t bytes. \"\u{1F1E6}\u{1F1FA}\" (🇦🇺) has count == 1 but utf8.count == 8. Pick the view that matches your need.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
let name = "Ada"
let greet = "Hello, \(name)!"
print(greet.uppercased())
print(name.count)
Try it Yourself »

Discussion

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