Dsl.swift

@dynamicMemberLookup
@dynamicCallable
class Dsl<UrlsType> {
    
    private let urls: UrlsType
    private var components: [String] = []
    
    init(urls: UrlsType) {
        self.urls = urls
    }
    
    subscript(dynamicMember keyPath: KeyPath<UrlsType, String>) -> Dsl {
        components.append(urls[keyPath: keyPath])

        return self
    }
    
    func dynamicallyCall(withArguments args: [String]) -> Dsl {
        components.append(contentsOf: args)
        
        return self
    }
    
    func make(replacements: [String: String] = [:]) -> String {
        return components.joined(separator: "/")
    }
}

struct ProfileUrls {
    
    let user = "user"
    let posts = "posts"
}
let dsl = Dsl(urls: ProfileUrls())
let postId = "123"
dsl.user.posts(postId).make()// user/posts/123