Classe to manage safely requests / Store them if it generates an error and send back when connexion came back or when user choose

DegradedMode.swift

//
//  DegradedMode.swift
//
//  Created by Maxime Charruel on 25/07/2017.
//  Copyright © 2017 Maxime Charruel. All rights reserved.
//
// DegradedMode allow you to sent safely requests and prevent error cases (e.g. timeout, connexion 
// issues, ...).
// When a request failed, it is stored in UserDefault and send back it when user choose to or
// automatically when connexion come back
// Just call DegradedMode.shared.sendRequest to send safely requests
// And DegradedMode.shared.trySendRequestsNotSent if you want to force send back

import Alamofire
import SwiftyJSON

open class DegradedMode {
    
    private var reachability: Reachability!
    private var requestItemsToSend: [RequestItem] = []
    
    /// Singleton
    public static let shared : DegradedMode = {
        let instance = DegradedMode.init()
        return instance
    }()
    
    /// On init, get userDefaults requests not sended
    public required init() {
        let userDefaults = UserDefaults.standard
        if userDefaults.object(forKey: "requestItemsToSend") != nil {
            let decodedRequestItemsToSend  = userDefaults.object(forKey: "requestItemsToSend") as! Data
            requestItemsToSend = NSKeyedUnarchiver.unarchiveObject(with: decodedRequestItemsToSend) as! [RequestItem]
        }
    }
    
    /// Save requests not sended in userDefaults
    open func saveRequestItemsToSend () {
        let userDefaults = UserDefaults.standard
        let encodedData: Data = NSKeyedArchiver.archivedData(withRootObject: DegradedMode.shared.requestItemsToSend)
        userDefaults.set(encodedData, forKey: "requestItemsToSend")
        userDefaults.synchronize()
    }
    
    /// Start Observing Network changes
    open func startObservingNetwork () {
        NotificationCenter.default.addObserver(self, selector: #selector(reachabilityChanged), name: ReachabilityChangedNotification, object: nil)
        
        self.reachability = Reachability.init()
        do {
            try self.reachability.startNotifier()
        } catch {
            print("Couldn't start observing, something went wrong")
        }
    }
    
    /// On Network changes
    ///
    /// - Parameter notification: NotificationCenter notification
    @objc func reachabilityChanged(notification: Notification) {
        let reachability = notification.object as! Reachability
        if reachability.isReachable {
            print("Network reachable")
            trySendRequestsNotSent()
        } else {
            print("Network not reachable")
        }
    }
    
    /// Method called when you want to send a request, prevents its fail and store it. If request 
    /// doesn't fail, it does nothing.
    /// You should call this method everytime you want to send a request, it will does the job
    ///
    /// - Parameters:
    ///   - requestItem: your request formatted with Object RequestItem
    ///   - completionHandler: return JSONData answer and error (if there is)
    open func sendRequest (requestItem: RequestItem, completionHandler: @escaping (JSON, Error?) -> ()) {
        Alamofire.request(requestItem.urlToCall, method: requestItem.method, parameters: requestItem.params, headers: requestItem.headers).responseJSON { response in
            
            switch response.result {
            case .success:
                // Do nothing
                break
            case .failure:
                // Something went wrong, request added to requests to send later
                self.addRequestItemToSendLater(requestItem: requestItem)
                break
            }
            completionHandler(JSON(data: response.data!), response.result.error!)
        }
        
        APIController.shared.sendRequest(requestItem: requestItem, completionHandler: { jsonData, error in
            if error != nil {
                // Something went wrong, request added to requests to send later
                self.addRequestItemToSendLater(requestItem: requestItem)
            }
            completionHandler(jsonData, error)
        })
    }
    
    /// Private method used to store not sended request and add it to UserDefaults Session
    ///
    /// - Parameter requestItem: your request formatted with Object RequestItem
    private func addRequestItemToSendLater (requestItem: RequestItem) {
        requestItemsToSend.append(requestItem)
        saveRequestItemsToSend()
    }
    
    /// Method to send not sended requests, this method is automatically called when reachilibity 
    /// changed but you can force send back by calling this method
    ///
    /// - Returns: Array of Error, for requests which still have not been sent
    public func trySendRequestsNotSent (trySendRequestsNotSentCompletionHandler: @escaping ([Error]) -> () = { _ in }) {
        
        // If there is requests
        if !requestItemsToSend.isEmpty {
            let requestItemsToSendCopy = requestItemsToSend
            
            NSLog("Send list started")
            launchRequestsInOrder(requestItemsToSendCopy, 0, [], launchRequestsInOrderCompletionBlock: { index, errors in
                trySendRequestsNotSentCompletionHandler(errors)
            })
        }
        else {
            trySendRequestsNotSentCompletionHandler([])
        }
    }
    
    /// Private method to launch requests (still not sent !) in the same order there were stored
    ///
    /// - Parameters:
    ///   - requestItemsToSend: Array of RequestItem to send
    ///   - index: the current index of request sent
    ///   - errors: Array of error, updated by each request if there is an error
    ///   - launchRequestsInOrderCompletionBlock: Completion executed when launch is done
    private func launchRequestsInOrder (_ requestItemsToSend: [RequestItem], _ index: Int, _ errors: [Error], launchRequestsInOrderCompletionBlock: @escaping (_ index: Int, _ errors: [Error] ) -> Void) {
        
        executeRequest(requestItemsToSend, index, errors, executeRequestCompletionBlock: { currentIndex, errors in
            if currentIndex < requestItemsToSend.count {
                // We didn't reach last request, launch next request
                self.launchRequestsInOrder(requestItemsToSend, currentIndex, errors, launchRequestsInOrderCompletionBlock: { index, errors in
                    
                    launchRequestsInOrderCompletionBlock(currentIndex, errors)
                })
            }
            else {
                // We parse and send all requests
                NSLog("Send list finished")
                launchRequestsInOrderCompletionBlock(currentIndex, errors)
            }
        })
    }
    
    /// Private method called to send a specific request
    ///
    /// - Parameters:
    ///   - requestItemsToSend: your request formatted with Object RequestItem
    ///   - index: the current index of request sent
    ///   - errors: Array of errors
    ///   - executeRequestCompletionBlock: Completion executed when request has been sent
    private func executeRequest (_ requestItemsToSend: [RequestItem], _ index: Int, _ errors: [Error], executeRequestCompletionBlock: @escaping (_ index: Int, _ errors: [Error]) -> Void) {
        NSLog("Send request %d", index)
        Alamofire.request(requestItemsToSend[index].urlToCall, method: requestItemsToSend[index].method, parameters: requestItemsToSend[index].params, headers: requestItemsToSend[index].headers).responseJSON { response in

            var errors: [Error] = errors
            switch response.result {
            case .success:
                // Request sended successfully, we can remove it from not sended request array
                self.requestItemsToSend.remove(at: index)
                break
            case .failure:
                // Still not send we append arror
                errors.append(response.result.error!)
                break
            }
            NSLog("Receive request %d", index)
            executeRequestCompletionBlock(index+1, errors)
        }
    }
}

Reachability.swift

/*
 Copyright (c) 2014, Ashley Mills
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
 
 1. Redistributions of source code must retain the above copyright notice, this
 list of conditions and the following disclaimer.
 
 2. Redistributions in binary form must reproduce the above copyright notice,
 this list of conditions and the following disclaimer in the documentation
 and/or other materials provided with the distribution.
 
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
 */

import SystemConfiguration
import Foundation

public enum ReachabilityError: Error {
    case FailedToCreateWithAddress(sockaddr_in)
    case FailedToCreateWithHostname(String)
    case UnableToSetCallback
    case UnableToSetDispatchQueue
}

public let ReachabilityChangedNotification = NSNotification.Name("ReachabilityChangedNotification")

func callback(reachability:SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutableRawPointer?) {
    
    guard let info = info else { return }
    
    let reachability = Unmanaged<Reachability>.fromOpaque(info).takeUnretainedValue()
    
    DispatchQueue.main.async {
        reachability.reachabilityChanged()
    }
}

public class Reachability {
    
    public typealias NetworkReachable = (Reachability) -> ()
    public typealias NetworkUnreachable = (Reachability) -> ()
    
    public enum NetworkStatus: CustomStringConvertible {
        
        case notReachable, reachableViaWiFi, reachableViaWWAN
        
        public var description: String {
            switch self {
            case .reachableViaWWAN: return "Cellular"
            case .reachableViaWiFi: return "WiFi"
            case .notReachable: return "No Connection"
            }
        }
    }
    
    public var whenReachable: NetworkReachable?
    public var whenUnreachable: NetworkUnreachable?
    public var reachableOnWWAN: Bool
    
    // The notification center on which "reachability changed" events are being posted
    public var notificationCenter: NotificationCenter = NotificationCenter.default
    
    public var currentReachabilityString: String {
        return "\(currentReachabilityStatus)"
    }
    
    public var currentReachabilityStatus: NetworkStatus {
        guard isReachable else { return .notReachable }
        
        if isReachableViaWiFi {
            return .reachableViaWiFi
        }
        if isRunningOnDevice {
            return .reachableViaWWAN
        }
        
        return .notReachable
    }
    
    fileprivate var previousFlags: SCNetworkReachabilityFlags?
    
    fileprivate var isRunningOnDevice: Bool = {
        #if (arch(i386) || arch(x86_64)) && os(iOS)
            return false
        #else
            return true
        #endif
    }()
    
    fileprivate var notifierRunning = false
    fileprivate var reachabilityRef: SCNetworkReachability?
    
    fileprivate let reachabilitySerialQueue = DispatchQueue(label: "uk.co.ashleymills.reachability")
    
    required public init(reachabilityRef: SCNetworkReachability) {
        reachableOnWWAN = true
        self.reachabilityRef = reachabilityRef
    }
    
    public convenience init?(hostname: String) {
        
        guard let ref = SCNetworkReachabilityCreateWithName(nil, hostname) else { return nil }
        
        self.init(reachabilityRef: ref)
    }
    
    public convenience init?() {
        
        var zeroAddress = sockaddr()
        zeroAddress.sa_len = UInt8(MemoryLayout<sockaddr>.size)
        zeroAddress.sa_family = sa_family_t(AF_INET)
        
        guard let ref: SCNetworkReachability = withUnsafePointer(to: &zeroAddress, {
            SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
        }) else { return nil }
        
        self.init(reachabilityRef: ref)
    }
    
    deinit {
        stopNotifier()
        
        reachabilityRef = nil
        whenReachable = nil
        whenUnreachable = nil
    }
}

public extension Reachability {
    
    // MARK: - *** Notifier methods ***
    func startNotifier() throws {
        
        guard let reachabilityRef = reachabilityRef, !notifierRunning else { return }
        
        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = UnsafeMutableRawPointer(Unmanaged<Reachability>.passUnretained(self).toOpaque())
        if !SCNetworkReachabilitySetCallback(reachabilityRef, callback, &context) {
            stopNotifier()
            throw ReachabilityError.UnableToSetCallback
        }
        
        if !SCNetworkReachabilitySetDispatchQueue(reachabilityRef, reachabilitySerialQueue) {
            stopNotifier()
            throw ReachabilityError.UnableToSetDispatchQueue
        }
        
        // Perform an initial check
        reachabilitySerialQueue.async {
            self.reachabilityChanged()
        }
        
        notifierRunning = true
    }
    
    func stopNotifier() {
        defer { notifierRunning = false }
        guard let reachabilityRef = reachabilityRef else { return }
        
        SCNetworkReachabilitySetCallback(reachabilityRef, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachabilityRef, nil)
    }
    
    // MARK: - *** Connection test methods ***
    var isReachable: Bool {
        
        guard isReachableFlagSet else { return false }
        
        if isConnectionRequiredAndTransientFlagSet {
            return false
        }
        
        if isRunningOnDevice {
            if isOnWWANFlagSet && !reachableOnWWAN {
                // We don't want to connect when on 3G.
                return false
            }
        }
        
        return true
    }
    
    var isReachableViaWWAN: Bool {
        // Check we're not on the simulator, we're REACHABLE and check we're on WWAN
        return isRunningOnDevice && isReachableFlagSet && isOnWWANFlagSet
    }
    
    var isReachableViaWiFi: Bool {
        
        // Check we're reachable
        guard isReachableFlagSet else { return false }
        
        // If reachable we're reachable, but not on an iOS device (i.e. simulator), we must be on WiFi
        guard isRunningOnDevice else { return true }
        
        // Check we're NOT on WWAN
        return !isOnWWANFlagSet
    }
    
    var description: String {
        
        let W = isRunningOnDevice ? (isOnWWANFlagSet ? "W" : "-") : "X"
        let R = isReachableFlagSet ? "R" : "-"
        let c = isConnectionRequiredFlagSet ? "c" : "-"
        let t = isTransientConnectionFlagSet ? "t" : "-"
        let i = isInterventionRequiredFlagSet ? "i" : "-"
        let C = isConnectionOnTrafficFlagSet ? "C" : "-"
        let D = isConnectionOnDemandFlagSet ? "D" : "-"
        let l = isLocalAddressFlagSet ? "l" : "-"
        let d = isDirectFlagSet ? "d" : "-"
        
        return "\(W)\(R) \(c)\(t)\(i)\(C)\(D)\(l)\(d)"
    }
}

fileprivate extension Reachability {
    
    func reachabilityChanged() {
        
        let flags = reachabilityFlags
        
        guard previousFlags != flags else { return }
        
        let block = isReachable ? whenReachable : whenUnreachable
        block?(self)
        
        self.notificationCenter.post(name: ReachabilityChangedNotification, object:self)
        
        previousFlags = flags
    }
    
    var isOnWWANFlagSet: Bool {
        #if os(iOS)
            return reachabilityFlags.contains(.isWWAN)
        #else
            return false
        #endif
    }
    var isReachableFlagSet: Bool {
        return reachabilityFlags.contains(.reachable)
    }
    var isConnectionRequiredFlagSet: Bool {
        return reachabilityFlags.contains(.connectionRequired)
    }
    var isInterventionRequiredFlagSet: Bool {
        return reachabilityFlags.contains(.interventionRequired)
    }
    var isConnectionOnTrafficFlagSet: Bool {
        return reachabilityFlags.contains(.connectionOnTraffic)
    }
    var isConnectionOnDemandFlagSet: Bool {
        return reachabilityFlags.contains(.connectionOnDemand)
    }
    var isConnectionOnTrafficOrDemandFlagSet: Bool {
        return !reachabilityFlags.intersection([.connectionOnTraffic, .connectionOnDemand]).isEmpty
    }
    var isTransientConnectionFlagSet: Bool {
        return reachabilityFlags.contains(.transientConnection)
    }
    var isLocalAddressFlagSet: Bool {
        return reachabilityFlags.contains(.isLocalAddress)
    }
    var isDirectFlagSet: Bool {
        return reachabilityFlags.contains(.isDirect)
    }
    var isConnectionRequiredAndTransientFlagSet: Bool {
        return reachabilityFlags.intersection([.connectionRequired, .transientConnection]) == [.connectionRequired, .transientConnection]
    }
    
    var reachabilityFlags: SCNetworkReachabilityFlags {
        
        guard let reachabilityRef = reachabilityRef else { return SCNetworkReachabilityFlags() }
        
        var flags = SCNetworkReachabilityFlags()
        let gotFlags = withUnsafeMutablePointer(to: &flags) {
            SCNetworkReachabilityGetFlags(reachabilityRef, UnsafeMutablePointer($0))
        }
        
        if gotFlags {
            return flags
        } else {
            return SCNetworkReachabilityFlags()
        }
    }
}

RequestItem.swift

//
//  RequestItem.swift
//
//  Created by Maxime Charruel on 01/09/2017.
//  Copyright © 2017 Acheteza. All rights reserved.
//

import Alamofire

public class RequestItem: NSObject, NSCoding {
    
    public var url: String = ""
    public var method: HTTPMethod = .get
    public var params: [String: String] = [:]
    public var headers: [String: String] = [:]

    /// Initializer
    ///
    /// - Parameters:
    ///   - url: url to call
    ///   - method: method .get / .post / ...
    ///   - params: parameters
    ///   - headers: headers
    public convenience init (url: String, method: HTTPMethod, params: [String: String], headers: [String: String]) {
        self.init()
        self.url = url
        self.method = method
        self.params = params
        self.headers = headers
    }
    
    /// Decode requests from UserDefaults
    ///
    /// - Parameter aDecoder: coder
    required convenience public init(coder aDecoder: NSCoder) {
        self.init()
        url = aDecoder.decodeObject(forKey: "url") as! String
        method = HTTPMethod(rawValue: aDecoder.decodeObject(forKey: "method") as! String)!
        params = aDecoder.decodeObject(forKey: "params") as! [String: String]
        headers = aDecoder.decodeObject(forKey: "headers") as! [String: String]
    }
    
    /// Encode requests from UserDefaults
    ///
    /// - Parameter aCoder: coder
    open func encode(with aCoder: NSCoder) {
        aCoder.encode(url, forKey: "url")
        aCoder.encode(method.rawValue, forKey: "method")
        aCoder.encode(params, forKey: "params")
        aCoder.encode(params, forKey: "headers")
    }
}