Running throwing functions

Swift doesn’t like errors to happen when your program runs, which means it won’t let you run an error-throwing function by accident.

Instead, you need to call these functions using three new keywords: do starts a section of code that might cause problems, try is used before every function that might throw an error, and catch lets you handle errors gracefully.

If any errors are thrown inside the do block, execution immediately jumps to the catch block. Let’s try calling checkPassword() with a parameter that throws an error:

do {
    try checkPassword("password")
    print("That password is good!")
} catch {
    print("You can't use that password.")
}

When that code runs, “You can’t use that password” is printed, but “That password is good” won’t be – that code will never be reached, because the error is thrown.

SPONSORED Would you describe yourself as knowledgeable, but struggling when you have to come up with your own code? Fernando Olivares has a new book containing iOS rules you can immediately apply to your coding habits to see dramatic improvements, while also teaching applied programming fundamentals seen in refactored code from published apps.

Try the book!

Sponsor Hacking with Swift and reach the world's largest Swift community!