Why actors prevent data races in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an actor in Swift.

Swift

actor [1] {
    var count = 0
}

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Aclass

BCounter

Cstruct

Denum

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'class' or 'struct' instead of 'actor' to declare an actor.

The keyword actor declares an actor type named Counter.

2fill in blank

medium

Complete the code to safely increment the count inside the actor.

Swift

actor Counter {
    var count = 0
    func increment() {
        [1]
    }
}

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Aself.count = count + 1

Bcount += 1

Ccount = count + 1

Dself.count += 1

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting 'self.' before 'count' inside the actor method.

Inside an actor, use self.count += 1 to modify the property safely.

3fill in blank

hard

Fix the error in calling the actor's method asynchronously.

Swift

let counter = Counter()
Task {
    await [1].increment()
}

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Acounter

BCounter

Cself

Dincrement

Attempts:

3 left

💡 Hint

Common Mistakes

Using the actor type name instead of the instance to call the method.

You must call the method on the actor instance counter using await because actor methods are asynchronous.

4fill in blank

hard

Fill both blanks to define an actor with a method that returns the count.

Swift

actor [1] {
    var count = 0
    func getCount() async -> [2] {
        return count
    }
}

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ASafeCounter

BInt

CString

DDouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong return type like String or Double for the count.

The actor is named SafeCounter and the method returns an Int representing the count.

5fill in blank

hard

Fill all three blanks to create an actor that prevents data races by isolating state and providing safe access.

Swift

actor [1] {
    private var value: [2] = 0
    func updateValue(to newValue: [3]) {
        value = newValue
    }
}

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ADataGuard

BInt

CString

DDouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types for the variable and method parameter.

The actor DataGuard isolates the Int state value and safely updates it through a method, preventing data races.