A simple API to fetch gists on GitHub

GistAPI.swift

//
//  GistAPI.swift
//  Gists
//
//  Created by Raymond Law on 2/5/16.
//  Copyright © 2016 Clean Swift. All rights reserved.
//

import Foundation

class GistAPI
{
  private let user = "rayvinly"
  private var url: NSURL? {
    return NSURL(string: "https://api.github.com/users/\(user)/gists")
  }
  
  func fetchGists(completionHandler: (gists: [Gist]?, error: ErrorType?) -> Void)
  {
    let config = NSURLSessionConfiguration.defaultSessionConfiguration()
    let session = NSURLSession(configuration: config)
    if let url = url {
      session.dataTaskWithURL(url) { (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
        if let error = error {
          dispatch_async(dispatch_get_main_queue(), {
            completionHandler(gists: nil, error: error)
          })
        }
        if let data = data {
          let gists = self.parseGists(data)
          dispatch_async(dispatch_get_main_queue(), {
            completionHandler(gists: gists, error: nil)
          })
        }
        }.resume()
    }
  }
  
  private func parseGists(data: NSData) -> [Gist]
  {
    var gists = [Gist]()
    do {
      let json = try NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments)
      if let gistsJSON = json as? [[String: AnyObject]] {
        for gistJSON in gistsJSON {
          let id = gistJSON["id"] as? String
          let createdAtString = gistJSON["created_at"] as? String
          let createdAtDate = parseCreatedAt(createdAtString)
          let user = gistJSON["owner"]?["login"] as? String
          let desc = gistJSON["description"] as? String
          if let filesJSON = gistJSON["files"] as? [String: NSDictionary] {
            for fileJSON in filesJSON.values {
              if let rawURL = fileJSON["raw_url"] as? String {
                let url = NSURL(string: rawURL)
                let gist = Gist(id: id, createdAt: createdAtDate, user: user, desc: desc, url: url, content: nil)
                gists.append(gist)
              }
            }
          }
        }
      }
    } catch {
    }
    return gists
  }
  
  private func parseCreatedAt(date: String?) -> NSDate?
  {
    guard let date = date else { return nil }
    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"
    return dateFormatter.dateFromString(date)
  }
}