@resultBuilder attribute in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a simple result builder named Builder.

Swift

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

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

Amain

BpropertyWrapper

CresultBuilder

Davailable

Attempts:

3 left

💡 Hint

Common Mistakes

Using '@propertyWrapper' instead of '@resultBuilder'.

Forgetting the '@' symbol before 'resultBuilder'.

The @resultBuilder attribute is used to define a custom builder type that can combine multiple components into one result.

2fill in blank

medium

Complete the code to use the Builder result builder in a function.

Swift

@Builder
func buildText() -> String {
    [1] "Hello"
    "World"
}

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

Aprint

Breturn

Cyield

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'yield' which is for generators, not result builders.

Using 'print' which outputs to console but does not return a value.

Inside a function using a result builder, you use 'return' to provide components that the builder will combine.

3fill in blank

hard

Fix the error in the buildBlock method to correctly combine Int values.

Swift

@resultBuilder
struct IntBuilder {
    static func buildBlock(_ components: Int[1]) -> Int {
        components.reduce(0, +)
    }
}

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A...

C...Int...

D...Int

Attempts:

3 left

💡 Hint

Common Mistakes

Writing '...Int' which is invalid syntax.

Using '...Int...' which is not valid.

The buildBlock method takes a variadic parameter of Ints, which is written as 'Int...'.

4fill in blank

hard

Fill both blanks to create a result builder that combines strings with a space.

Swift

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

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

A...

B.joined(

C)

D.joined

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses incorrectly around 'joined'.

Forgetting the variadic '...'.

The buildBlock method takes a variadic String parameter 'String...' and calls '.joined(separator: " ")' on the components.

5fill in blank

hard

Fill all three blanks to define a result builder that filters out empty strings and joins the rest with commas.

Swift

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

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

A...

Bcomponent

Cjoined

Dcomponents

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'components' inside the filter closure instead of the singular parameter.

Forgetting to use 'joined' method to combine strings.

The buildBlock method takes a variadic String parameter 'String...'. The filter closure uses 'component.isEmpty == false' to exclude empty strings. Then it calls 'joined(separator: ",")' to combine the filtered strings.