Checks for a new version from a server and prompts the user to install it. Great for enterprise builds.

EAVersionChecker.swift

//
//  EAVersionChecker.swift
//  Copyright (c) 2015 Oven Bits. All rights reserved.
//

import Foundation

class EAVersionChecker {
    var versionManifestURL: String = ""
    var currentLocalVersion: String { return "\(localSVS).\(localBuild)" }
    
    private var infoDictionary: [NSObject:AnyObject]! { return NSBundle.mainBundle().infoDictionary! }
    private var localSVS: String { return infoDictionary["CFBundleShortVersionString"] as! String }
    private var localBuild: String { return infoDictionary["CFBundleVersion"] as! String }
    private var session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
    
    static let sharedChecker: EAVersionChecker = EAVersionChecker()
    
    func checkForUpdates(completion: (NSURL?, NSError?) -> Void) {
        if let url = NSURL(string: versionManifestURL) {
            let task = session.dataTaskWithURL(url) { data, resp, error in
                if let error = error {
                    completion(nil, error)
                    return
                }
                
                self.handleServerResponse(data, completion: completion)
            }
            task.resume()
            return
        }
        
        completion(nil, nil)
    }
    
    private func handleServerResponse(data: NSData, completion: (NSURL?, NSError?) -> Void) {
        if let parsed = NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments, error: nil) as? [NSObject:AnyObject] {
            let json = JSON(parsed)
            
            let version = json["latestVersion"].string
            if !self.versionStringIsGreaterThanInternalVersion(version) {
                DDLogInfo("Version retrieved from server (\(version)) is older, or current.")
                completion(nil, nil)
                return
            }
            if let updateURLString = json["updateUrl"].string, updateURL = NSURL(string: updateURLString) {
                DDLogWarn("Version retrieved from server (\(version)) is newer than \(self.currentLocalVersion). Requesting update.")
                completion(updateURL, nil)
                return
            }
        } else {
            let jsonString = NSString(data: data, encoding: NSUTF8StringEncoding)
            DDLogError("Encountered error parson JSON: \(jsonString)")
        }
    }
    
    private func versionStringIsGreaterThanInternalVersion(versionString: String?) -> Bool {
        if let result = versionString?.compare(currentLocalVersion, options: NSStringCompareOptions.NumericSearch) {
            return result == .OrderedDescending
        }
        return false
    }
}

Usage.swift

let manager = EAVersionChecker.sharedChecker
manager.versionManifestURL = "https://remote.path/to/version.json"
manager.checkForUpdates { urlToOpen, error in
    if let error = error {
        println("An error occurred checking for the latest version: \(error.localizedDescription)")
        return
    }
    
    if let urlToOpen = urlToOpen, rootVC = self.window?.rootViewController {
        if UIApplication.sharedApplication().canOpenURL(urlToOpen) {
            UIApplication.sharedApplication().openURL(urlToOpen)
        }
    }
}