Swift ArrayBuilder resultBuilder

gistfile1.txt

// Use to create an Array of elements in a result builder
//
// Best used with a typealias:
// typealias StringBuilder = ArrayBuilder<String>

@resultBuilder
public struct ArrayBuilder<Element> {

    public static func buildBlock(_ components: [Element]...) -> [Element] {
        components.flatMap { $0 }
    }

    public static func buildExpression(_ expression: Element) -> [Element] {
        [expression]
    }

    public static func buildOptional(_ component: [Element]?) -> [Element] {
        component ?? []
    }

    public static func buildEither(first component: [Element]) -> [Element] {
        component
    }

    public static func buildEither(second component: [Element]) -> [Element] {
        component
    }

    public static func buildArray(_ components: [[Element]]) -> [Element] {
        components.flatMap { $0 }
    }
}