Swift:
Interpolating a string
How to:
Swift makes string interpolation a breeze with the \(variableName) syntax.
let name = "Jane"
let age = 28
let greeting = "Hello, \(name), you are \(age) years old."
print(greeting) // Output: Hello, Jane, you are 28 years old.You can even perform operations within the interpolation:
let apples = 3
let oranges = 5
let fruitSummary = "I have \(apples + oranges) pieces of fruit."
print(fruitSummary) // Output: I have 8 pieces of fruit.Deep Dive
Okay, let’s get a bit historical. String interpolation isn’t unique to Swift. It exists in many languages (like JavaScript, Python, etc.), but Swift’s version is type-safe meaning the compiler checks the types for you, reducing errors.
Before Swift 5, string interpolation was less powerful and more cumbersome. But Swift 5 introduced Extended String Interpolation, which allows you to customize string interpolation, bringing impressive flexibility.
Alternatives to string interpolation in Swift include concatenation using +, and the older String(format:) method. However, these are less convenient and, for format strings, harder to read.
Implementation details? With Swift’s string interpolation, you can customize how types are represented within strings by extending the StringInterpolation protocol. This means you can define how custom types are displayed during interpolation, which is super handy.
extension String.StringInterpolation {
mutating func appendInterpolation(_ value: Date) {
let formatter = DateFormatter()
formatter.dateStyle = .medium
appendLiteral(formatter.string(from: value))
}
}
let today = Date()
let dateString = "Today's date is \(today)."
print(dateString) // Output will be today's date in medium style formatting.See Also
To get the nitty-gritty on string interpolation, Swift’s documentation is golden:
For swirling deeper into formatting custom types: