An attempt at parsing Reddit using Codable

reddit.swift

class RedditManager {
    static let shared = RedditManager()
    
    private let session: URLSession
    
    private init() {
        let configuration = URLSessionConfiguration.default
        
        session = URLSession(configuration: configuration)
    }
    
    func posts(fromSubreddit subreddit: String, completion: @escaping ([RedditPost]?) -> Void) {
        let apiURL = URL(string: "https://reddit.com/r/\(subreddit).json?raw_json=1")!
        
        session.dataTask(with: apiURL) { (data, response, error) in
            guard let data = data else { return }
            
            do {
                let redditPostOuter = try JSONDecoder().decode(RedditPostOuter.self, from: data)
                completion(redditPostOuter.posts)
            } catch {
                print(error)
            }
        }.resume()
    }
}

private struct RedditPostOuter: Decodable {
    let data: RedditPostOuterData?
    
    var posts: [RedditPost]? {
        return data?.children?.map { $0.data }
    }
}

private struct RedditPostOuterData: Decodable {
    let children: [RedditPostListingChild]?
}

private struct RedditPostListingChild: Decodable {
    let data: RedditPost
}

struct RedditPost: Decodable {
    let title: String
    let score: Int
}

Example JSON (long): http://reddit.com/r/itookapicture.json?raw_json=1