Error Handling (do-try-catch)

In this lesson you will learn error handling in Swift with do-try-catch, so an unexpected failure does not bring your whole program down. This is for anyone searching for "Swift do try catch how to use".

Marking a function throws states that it may throw an error, and the caller catches it with do / try / catch. Swift manages errors through the type system, so a missing error handler is caught at compile time - a genuinely safe mechanism.

The sample code defines the kinds of error in the MyError enum and throws with throw MyError.divideByZero inside divide() when asked to divide by zero. The caller calls it with try inside a do block and catches the error in catch.

A common stumbling block for beginners is forgetting the try. Omitting it is a compile error, which is exactly what stops error handling from being overlooked, though it takes a moment to get used to.

In real-world development this do-try-catch style is used widely for anything that can fail, such as file operations and network calls.

📖 Reference code

enum MyError: Error {
    case divideByZero
}

func divide(_ a: Int, _ b: Int) throws -> Int {
    if b == 0 { throw MyError.divideByZero }
    return a / b
}

do {
    print(try divide(10, 2))
    print(try divide(10, 0))
} catch {
    print("An error occurred")
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Swift directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).