Throwing functions with throws in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the throws keyword mean in a Swift function?

It means the function can produce an error that must be handled by the caller using try, try?, or try!.

beginner

How do you call a function that can throw an error?

You use the try keyword before the function call, and handle errors with do-catch or propagate them further.

beginner

What is the purpose of the do-catch block in Swift?

It lets you run code that might throw errors and catch those errors to handle them safely.

beginner

What happens if you call a throwing function without try?

The code will not compile because Swift requires explicit handling of possible errors.

intermediate

Explain the difference between try? and try!.

try? converts the error into an optional value (nil if error), while try! forces the call and crashes if an error occurs.

What keyword must a Swift function include if it can throw an error?

A catch

B try

C throws

D error

The throws keyword marks a function that can throw errors.

How do you handle errors when calling a throwing function?

A Use <code>throws</code> when calling

B Just call the function normally

C Use <code>catch</code> without <code>try</code>

D Use <code>try</code> and <code>do-catch</code>

You must use try and handle errors with do-catch or propagate them.

What does try? do when a throwing function fails?

A Returns nil instead of throwing

B Crashes the program

C Ignores the error silently

D Throws the error normally

try? returns an optional nil if an error occurs.

What happens if you call a throwing function without try?

A Compilation error

B Runs normally

C Runtime error

D Warning but runs

Swift requires try to call throwing functions; otherwise, it won't compile.

Which block is used to catch errors thrown by a function?

A try-catch

B do-catch

C throw-catch

D if-else

Swift uses do-catch blocks to catch and handle errors.

Describe how to write and call a throwing function in Swift.

Think about marking the function and how the caller must handle errors.

Explain the difference between try, try?, and try! when calling throwing functions.

Consider how each handles errors differently.