Existential types (any keyword) in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable that can hold any type conforming to the protocol.

Swift

var value: [1] CustomStringConvertible

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

Aany

Bsome

Clet

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'some' instead of 'any' which is for opaque types.

Using 'var' or 'let' inside the type declaration.

The 'any' keyword is used to declare an existential type that can hold any value conforming to the protocol.

2fill in blank

medium

Complete the function signature to accept any type conforming to Equatable.

Swift

func compare(_ a: [1] Equatable, _ b: [1] Equatable) -> Bool

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

Alet

Bsome

Cvar

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'some' which is for opaque types and not allowed in parameter positions.

Omitting the keyword and causing a compile error.

The 'any' keyword is used to accept any value conforming to the Equatable protocol as an existential type.

3fill in blank

hard

Fix the error in the code by adding the correct keyword for existential types.

Swift

let description: [1] CustomStringConvertible = "Hello"

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

Asome

Bvar

Cany

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'some' which is for opaque types and incompatible here.

Omitting the keyword causing a compiler error.

The 'any' keyword is required to declare an existential type variable holding a value conforming to CustomStringConvertible.

4fill in blank

hard

Complete the code to create a dictionary with keys as Strings and values as any type conforming to CustomStringConvertible.

Swift

let dict: [String: [1] CustomStringConvertible] = ["key":  "value"]

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

Aany

Bsome

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'some' which is for opaque types and not allowed here.

Omitting 'any' from the type declaration causing a compiler error.

The dictionary value type uses 'any' to indicate an existential type conforming to CustomStringConvertible. No keyword is needed before the string literal.

5fill in blank

hard

Fill both blanks to define a function returning any type conforming to Equatable and assign a value inside.

Swift

func getValue() -> [1] Equatable {
    let val: [2] Equatable = 42
    return  val
}

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

Aany

Dsome

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'some' which is for opaque types and incompatible here.

Adding 'any' in the return statement which is not needed.

The function return type and variable use 'any' for existential types. The return statement returns the variable directly without extra keywords.