Weak self and unowned self patterns in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture self weakly inside the closure.

Swift

someAsyncFunction { [[1] self] in
    print(self?.description ?? "No self")
}

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

Aweak

Bunowned

Cstrong

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'unowned' when self might be nil causes crashes.

Forgetting to capture self weakly leads to retain cycles.

Using weak captures self weakly, preventing retain cycles and allowing self to become nil.

2fill in blank

medium

Complete the code to safely unwrap weak self inside the closure.

Swift

someAsyncFunction { [weak self] in
    guard let [1] = self else { return }
    print([1].description)
}

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

AweakSelf

BselfStrong

Cself

DstrongSelf

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same name 'self' for the constant causes confusion.

Not unwrapping weak self leads to optional usage errors.

Assigning self to a strong constant like strongSelf inside the closure safely unwraps weak self.

3fill in blank

hard

Fix the error in the closure capture list to avoid a retain cycle.

Swift

someAsyncFunction { [[1] self] in
    print(self.description)
}

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

Aunowned

Bweak

Cstrong

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'strong' causes retain cycles.

Using 'weak' requires optional unwrapping.

Using unowned captures self without increasing retain count and assumes self will not be nil.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that filters and maps with weak self.

Swift

let results = items.compactMap { item in
    guard let [1] = self else { return nil }
    return item.value [2] 10 ? item.key : nil
}

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

AstrongSelf

B>

C<

Dself

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'self' directly without unwrapping weak self.

Using the wrong comparison operator.

Unwrap weak self as strongSelf and use the greater than operator to filter values above 10.

5fill in blank

hard

Fill both blanks to create a closure that captures unowned self and uses it safely.

Swift

someAsyncFunction { [[1] self] in
    let message = self.[2] + " is ready"
    print(message)
}

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

Aunowned

Bstatus

C)

Dweak

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'weak' requires optional unwrapping.

Forgetting to close the print statement causes syntax errors.

Capture self as unowned, access the status property, and close the print statement with a parenthesis.