Why result builders enable DSLs in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple result builder attribute.

Swift

@resultBuilder
struct [1] {
    static func buildBlock(_ components: String...) -> String {
        components.joined(separator: ", ")
    }
}

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

AMyBuilder

BbuildBlock

CResultBuilder

DDSLBuilder

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name instead of a struct name.

Using a reserved keyword as the builder name.

The struct name defines the result builder. Here, MyBuilder is the custom builder name.

2fill in blank

medium

Complete the code to apply the result builder to a function.

Swift

func buildList(@[1] content: () -> String) -> String {
    content()
}

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

ADSLBuilder

BResultBuilder

CMyBuilder

DbuildBlock

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name instead of the builder name.

Omitting the '@' symbol before the builder name.

The function parameter uses the custom result builder MyBuilder to enable DSL syntax inside the closure.

3fill in blank

hard

Fix the error in the result builder usage by completing the code.

Swift

let result = buildList {
    "Hello"
    [1] "World"
}

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A+

B-

C;

D,

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' to concatenate strings inside the builder closure.

Using semicolons which are not needed here.

Inside the result builder closure, separate expressions with commas to build the combined result.

4fill in blank

hard

Fill both blanks to create a DSL-like syntax that builds a list of items.

Swift

let list = buildList {
    [1] "Apple"
    [2] "Banana"
}

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

A"Orange"

B"Grape"

C,

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolons instead of commas.

Not adding a string literal in the first blank.

The blanks should be commas to separate items in the builder closure.

5fill in blank

hard

Fill all three blanks to define a result builder that combines strings with spaces and use it in a function.

Swift

@resultBuilder
struct [1] {
    static func buildBlock(_ components: String...) -> String {
        components[2]separator: " "[3]
    }
}

func greet(@MyBuilder content: () -> String) -> String {
    content()
}

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

AMyBuilder

Bjoined

C()

DbuildBlock

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect struct name that doesn't match the attribute.

Omitting parentheses after 'joined'.

The struct name is MyBuilder. The buildBlock method joins components with spaces using joined(separator: " ").