Rethrowing functions in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function that can rethrow errors from its closure parameter.

Swift

func perform(action: () throws -> Void) [1] {
    try action()
}

Drag options to blanks, or click blank then click option'

Arethrows

Bthrows

Ctry

Dthrowing

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'throws' instead of 'rethrows' causes the function to always throw.

Using 'try' or 'throwing' is not valid in function declaration.

The rethrows keyword allows the function to throw errors only if the closure parameter throws.

2fill in blank

medium

Complete the code to call a rethrowing function with a throwing closure.

Swift

[1] perform(action: {
    throw NSError(domain: "Error", code: 1)
})

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Ado

Btry

Cthrow

Dcatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'do' or 'catch' inside the closure parameter is incorrect here.

Forgetting 'try' causes a compile error.

You must use try before the closure call because it can throw an error.

3fill in blank

hard

Fix the error in the function declaration to correctly rethrow errors from the closure.

Swift

func execute(task: () throws -> Void) [1] {
    try task()
}

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Atry

Bthrows

Cthrow

Drethrows

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'throws' makes the function throw unconditionally.

Using 'throw' or 'try' in the declaration is invalid.

The function must be marked rethrows to propagate errors only if the closure throws.

4fill in blank

hard

Fill both blanks to define a rethrowing function that accepts a closure and calls it.

Swift

func runOperation(operation: () [1] -> Void) [2] {
    try operation()
}

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Athrows

Brethrows

Attempts:

3 left

💡 Hint

Common Mistakes

Marking the function as 'throws' instead of 'rethrows'.

Not marking the closure as 'throws'.

The closure parameter must be marked throws because it can throw errors, and the function must be rethrows to propagate those errors.

5fill in blank

hard

Fill all three blanks to create a rethrowing function that accepts a closure, calls it, and handles errors.

Swift

func handle(action: () [1] -> Void) [2] {
    do {
        try action()
    } catch {
        print([3])
    }
}

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Athrows

Brethrows

Cerror

Derrors

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'errors' instead of 'error' in the catch block.

Marking the function as 'throws' instead of 'rethrows'.

The closure is marked throws, the function rethrows, and the caught error is referenced as error inside the catch block.