Recursive Functions

In this lesson you will learn how to write a recursive function in Swift and understand how a function can call itself. This is for anyone searching for "Swift recursive function how to use".

A recursive function is a function that calls itself. It suits work that repeats the same calculation pattern, such as "n! = n x (n-1)!".

The sample code has factorial call itself as n * factorial(n - 1) to compute the factorial of 5. The stopping condition if n <= 1 { return 1 } is what makes the chain of calls come to an end.

A common stumbling block for beginners is forgetting that stopping condition. Without one, the function calls itself forever and the program crashes. Deep recursion also consumes a lot of stack, so it is worth considering whether a loop would do instead.

In real-world development, recursion is a natural fit for traversing tree structures and folder hierarchies.

📖 Reference code

func factorial(_ n: Int) -> Int {
    if n <= 1 { return 1 }
    return n * factorial(n - 1)
}
print(factorial(5))

✍️ 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).