Do-try-catch execution flow in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to call the function that might throw an error.

Swift

do {
    try [1]()
} catch {
    print("Error caught")
}

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

AriskyFunction

BsafeFunction

CprintError

DhandleError

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function that does not throw with try.

Forgetting to use try before the function call.

The try keyword is used before calling a function that can throw an error. Here, riskyFunction() is the function that might throw.

2fill in blank

medium

Complete the code to catch a specific error type.

Swift

do {
    try riskyFunction()
} catch [1] {
    print("Specific error caught")
}

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Alet error as NSError

Blet error as MyError

Clet error as String

Dlet error as Int

Attempts:

3 left

💡 Hint

Common Mistakes

Catching errors as the wrong type.

Using types that are not error types.

To catch a specific error type, you use catch let error as MyError. This matches errors of type MyError.

3fill in blank

hard

Fix the error in the catch block to properly handle the error.

Swift

do {
    try riskyFunction()
} catch {
    print([1])
}

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Aerror.message

Berror

Cerror.description

Derror.localizedDescription

Attempts:

3 left

💡 Hint

Common Mistakes

Using properties that do not exist on the error object.

Printing the error object directly without description.

Inside a catch block, error.localizedDescription gives a readable message about the error.

4fill in blank

hard

Fill both blanks to create a do-try-catch block that handles two different error types.

Swift

do {
    try riskyFunction()
} catch [1] {
    print("First error caught")
} catch [2] {
    print("Second error caught")
}

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Alet error as MyError

Blet error as NSError

Clet error as String

Dlet error as Int

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-error types in catch blocks.

Mixing up the order of catch blocks.

The first catch handles MyError type errors, the second handles NSError type errors.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps error codes to messages inside a do-try-catch block.

Swift

do {
    try riskyFunction()
} catch let error as [1] {
    let errorCode = error.code
    let errorMessages = [errorCode: [2]]
    print(errorMessages[[3]] ?? "Unknown error")
}

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

ANSError

Berror.localizedDescription

CerrorCode

DMyError

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong error types that don't have a code property.

Mixing keys and values in the dictionary.

Accessing the dictionary with wrong keys.

The catch block catches NSError. The dictionary maps errorCode to error.localizedDescription. The print statement accesses the message by errorCode.