Swift Strings

Creating and Interpolating Strings

A String is a sequence of characters wrapped in double quotes. Rather than concatenating pieces with +, Swift encourages string interpolation: writing \(expression) directly inside a string literal to embed any value, including the result of a computation.

let firstName = "Grace"
let lastName = "Hopper"
let fullName = "\(firstName) \(lastName)"
print(fullName) // Grace Hopper

let a = 6
let b = 7
print("\(a) times \(b) is \(a * b)") // 6 times 7 is 42

Common String Methods and Properties

String comes with a large standard library of methods for measuring, transforming, and inspecting text. count gives the number of characters, isEmpty checks for an empty string, uppercased() and lowercased() change case, and hasPrefix / hasSuffix check the edges of a string.

let message = "  Hello, Swift!  "

print(message.count)                     // 17, includes the spaces
print(message.trimmingCharacters(in: .whitespaces)) // "Hello, Swift!"
print(message.uppercased())               // "  HELLO, SWIFT!  "
print(message.contains("Swift"))          // true
print("Hello".hasPrefix("He"))            // true
print("Hello".hasSuffix("lo"))            // true

Combining and Splitting Strings

Strings can be joined with + or the append() method, and split apart with components(separatedBy:) or the newer split(separator:) method, which returns an array of substrings. These operations are essential when parsing user input or formatted text like CSV rows.

var greeting = "Hello"
greeting += ", " + "World!"
print(greeting) // "Hello, World!"

let csvLine = "apple,banana,cherry"
let fruits = csvLine.components(separatedBy: ",")
print(fruits) // ["apple", "banana", "cherry"]
print(fruits.count) // 3

• String interpolation \( ) embeds any expression directly inside a string literal.
• count, isEmpty — measure and check strings without extra imports.
• uppercased(), lowercased(), trimmingCharacters(in:) — common transformations.
• hasPrefix(_:), hasSuffix(_:), contains(_:) — substring checks.
• components(separatedBy:) — splits a string into an array of substrings.

Quick Reference: String Methods