Code sample #5 from my Medium post "Namespacing Swift code with nested types"

Namespacing-Swift-code-with-nested-types-4.swift

struct Post {
    let id: Int
    let author: User
    let title: String
    let text: String
}

extension Post {
    class TextFormatter {
        private let options: Set<Option>

        init(options: Set<Option>) {
            self.options = options
        }

        func formatTitle(for post: Post) -> String {
            return post.title.formatted(withOptions: options)
        }

        func formatText(for post: Post) -> String {
            return post.text.formatted(withOptions: options)
        }
    }
}

extension Post.TextFormatter {
    enum Option {
        case highlightNames
        case highlightLinks
    }
}