Protocol with associated types in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a protocol with an associated type named Item.

Swift

protocol Container {
    associatedtype [1]
}

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

AType

BElement

CItem

DContent

Attempts:

3 left

💡 Hint

Common Mistakes

Using a keyword like 'Type' which is reserved in Swift.

Choosing a name that is not descriptive or conventional.

The keyword associatedtype is followed by the name of the associated type, which in this case is Item.

2fill in blank

medium

Complete the code to declare a function in the protocol that returns an element of the associated type.

Swift

protocol Container {
    associatedtype Item
    func getItem() -> [1]
}

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AItem

BSelf

CAny

DVoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Any' which is too general.

Using 'Void' which means no return value.

The function returns the associated type Item, so the return type must be Item.

3fill in blank

hard

Fix the error in the struct declaration that conforms to the protocol with an associated type.

Swift

struct Box: Container {
    typealias [1] = String
    func getItem() -> String {
        return "Hello"
    }
}

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

AValue

BElement

CContent

DItem

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name like 'Element' which does not match the protocol.

Omitting the typealias entirely.

The protocol's associated type is named 'Item', so the typealias must match that name exactly.

4fill in blank

hard

Fill both blanks to complete the generic function that accepts any Container and returns its item.

Swift

func fetchItem<C: Container>(from container: C) -> [1] {
    return container.[2]()
}

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AC.Item

BgetItem

CItem

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using just 'Item' as return type without prefixing with generic parameter.

Calling a method name that does not exist like 'fetch()'.

The return type is the associated type of the generic parameter, written as 'C.Item'. The function to get the item is 'getItem()'.

5fill in blank

hard

Fill all three blanks to define a protocol with an associated type and a property of that type.

Swift

protocol Storage {
    associatedtype [1]
    var [2]: [3] { get set }
}

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

ADataType

Bdata

Dcontent

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the associated type and property type.

Using property names that do not match the code style.

The associated type is named 'DataType'. The property name is 'data' and its type is 'DataType'.