HTTP encapsulation

HTTP.swift

//
//  HTTP.swift
//  TableTest2
//
//  Created by Gazolla on 22/05/16.
//  Copyright © 2016 Gazolla. All rights reserved.
//

import Foundation
import UIKit

public class HTTP{
    
    static func GET(urlString:String, completion:(error:NSError?, data:NSData?)->Void){
        if let request = NSMutableURLRequest(urlString: urlString, method: .GET) {
            connectToServer(request, completion: completion)
        } else {
            let er = NSError(domain: "com.gazapps", code: 400, userInfo: [NSLocalizedDescriptionKey: NSHTTPURLResponse.localizedStringForStatusCode(400)])
            completion(error: er, data: nil)
        }
    }
    
    static func connectToServer(request:NSMutableURLRequest, completion:(error:NSError?, data:NSData?)->Void){
        startNetworkActivityIndicator()
        let config = NSURLSessionConfiguration.defaultSessionConfiguration()
        let session = NSURLSession(configuration: config)
        let task = session.dataTaskWithRequest(request) { (data, response, error) in
            stopNetworkActivityIndicator()
            if error != nil {
                completion(error: error, data: nil)
            } else if let httpResponse = response as? NSHTTPURLResponse {
                if 200...299 ~= httpResponse.statusCode {
                    completion(error: nil, data: data)
                } else {
                    let er = NSError(domain: "com.gazapps", code: httpResponse.statusCode, userInfo: [NSLocalizedDescriptionKey: NSHTTPURLResponse.localizedStringForStatusCode(httpResponse.statusCode)])
                    completion(error: er, data: nil)
                }
            }
        }
        task.resume()
    }
    
    static func startNetworkActivityIndicator(){
        dispatch_async(dispatch_get_main_queue()) {
            UIApplication.sharedApplication().networkActivityIndicatorVisible = true
        }
    }
    static func stopNetworkActivityIndicator(){
        dispatch_async(dispatch_get_main_queue()) {
            UIApplication.sharedApplication().networkActivityIndicatorVisible = false
        }
    }
}

extension NSMutableURLRequest {
    public convenience init?(urlString:String, method:HTTPVerb, body:NSData?=nil){
        if let url = NSURL(string:urlString) {
            self.init(URL:url)
            self.addValue("application/json", forHTTPHeaderField: "Content-Type")
            self.addValue("application/json", forHTTPHeaderField: "Accept")
            self.HTTPMethod = method.rawValue
            self.HTTPBody = body
        } else {
            return nil
        }
    }
}

public enum HTTPVerb:String {
    case GET
    case PUT
    case POST
    case DELETE
}

usage.swift

var items:[String]=[]

HTTP.GET("https://api.github.com/users/gazolla/repos") { (error, data) in
            if error != nil {
                print(error)
            }
            do {
                let json = try NSJSONSerialization.JSONObjectWithData(data!, options: [])
                for item in json as! [AnyObject]{
                    self.items.append(item["full_name"] as! String)
                }
            } catch {
                print(error)
            }
            dispatch_async(dispatch_get_main_queue(), { 
                self.tableView.reloadData()
            })
        }
}