swift class variable changing in same scope [duplicate] - swift

Question

I am making url calls thru an API that I created using swift as follows:
class API {
let apiEndPoint = "endpoint"
let apiUrl:String!
let consumerKey:String!
let consumerSecret:String!
var returnData = [:]
init(){
self.apiUrl = "https://myurl.com/"
self.consumerKey = "my consumer key"
self.consumerSecret = "my consumer secret"
}
func getOrders() -> NSDictionary{
return makeCall("orders")
}
func makeCall(section:String) -> NSDictionary{
let params = ["consumer_key":"key", "consumer_secret":"secret"]
Alamofire.request(.GET, "\(self.apiUrl)/\(self.apiEndPoint + section)", parameters: params)
.authenticate(user: self.consumerKey, password: self.consumerSecret)
.responseJSON { (request, response, data, error) -> Void in
println("error \(request)")
self.returnData = data! as NSDictionary
}
return self.returnData
}
}
I call this API in my UITableViewController to populate the table with SwiftyJSON library. However my returnData from the API is always empty. There is no problem with Alomofire calls as I can successfully retrieve value. My problem is how I am supposed to carry this data over to my table view controller?
var api = API()
api.getOrders()
println(api.returnData) // returnData is empty

Answer 1

As mattt points out, Alamofire is returning data asynchronously via a “completion handler” pattern, so you must do the same. You cannot just return the value immediately, but you instead want to change your method to not return anything, but instead use a completion handler closure pattern.
Nowadays, that might look like:
func getOrders(completionHandler: #escaping (Result<[String: Any]>) -> Void) {
performRequest("orders", completion: completionHandler)
}
func performRequest(_ section: String, completion: #escaping (Result<[String: Any]>) -> Void) {
let url = baseURL.appendingPathComponent(section)
let params = ["consumer_key": "key", "consumer_secret": "secret"]
Alamofire.request(url, parameters: params)
.authenticate(user: consumerKey, password: consumerSecret)
.responseJSON { response in
switch response.result {
case .success(let value as [String: Any]):
completion(.success(value))
case .failure(let error):
completion(.failure(error))
default:
fatalError("received non-dictionary JSON response")
}
}
}
Then, when you want to call it, you use this completion closure parameter (in trailing closure, if you want):
api.getOrders { result in
switch result {
case .failure(let error):
print(error)
case .success(let value):
// use `value` here
}
}
// but don't try to use the `error` or `value`, as the above closure
// has not yet been called
//

Answer 2

From the Alamofire README (emphasis added):
Networking in Alamofire is done asynchronously. Asynchronous programming may be a source of frustration to programmers unfamiliar with the concept, but there are very good reasons for doing it this way.
Rather than blocking execution to wait for a response from the server, a callback is specified to handle the response once it's received. The result of a request is only available inside the scope of a response handler. Any execution contingent on the response or data received from the server must be done within a handler.

Answer 3

Following is the complete flow for performing the 'Login Action' using Alamofire and Swift.
Alamofire v3.3
Swift 2.2
Xcode 7.3
I have used GCD and MBProgressHUD for my own convenience. Refactor and use as you like :)
func loginBtnTapped(sender: AnyObject) {
MBProgressHUD.showHUDAddedTo(self.view, animated: true)
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
let loginInfo : Dictionary<String,AnyObject> = ["email":"abc#g.com","password":"abc123"]
self.loginUser(loginInfo) { responseObject, error in
print("\(responseObject) \n \(error) ")
// Parsing JSON Below
let status = Int(responseObject?.objectForKey("status") as! String)
if status == 1 {
// Login Successfull...Move To New VC
}
else {
print(responseObject?.objectForKey("message"))! as! String)
}
return
}
dispatch_async(dispatch_get_main_queue()) {
MBProgressHUD.hideHUDForView(self.view, animated: true)
}
}
}
func loginUser(parameters:NSDictionary, completionHandler: (NSDictionary?, NSError?) -> ()) {
self.postRequest("http://qa.company.com/project/index.php/user/login",
paramDict: parameters as? Dictionary<String, AnyObject>,
completionHandler: completionHandler)
}
func postRequest(urlString: String, paramDict:Dictionary<String, AnyObject>? = nil,
completionHandler: (NSDictionary?, NSError?) -> ()) {
Alamofire.request(.POST, urlString, parameters: paramDict)
.responseJSON { response in
switch response.result {
case .Success(let JSON):
completionHandler(JSON as? NSDictionary, nil)
case .Failure(let error):
completionHandler(nil, error)
}
}
}

Answer 4

Details
xCode 9.1, Swift 4
Features:
Easy readable code
Ready templates (it's easy to add more requests)
Embedded solution with asynchronous data processing
Full examples
Sample 1
Return data using closure
Data1.searchRequest(term: "jack johnson") { json, error in
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
Full sample 1
Data class
import Alamofire
class Data1 {
static fileprivate let queue = DispatchQueue(label: "requests.queue", qos: .utility)
static fileprivate let mainQueue = DispatchQueue.main
fileprivate class func make(request: DataRequest, closure: #escaping (_ json: [String: Any]?, _ error: Error?)->()) {
request.responseJSON(queue: Data1.queue) { response in
// print(response.request ?? "nil") // original URL request
// print(response.response ?? "nil") // HTTP URL response
// print(response.data ?? "nil") // server data
//print(response.result ?? "nil") // result of response serialization
switch response.result {
case .failure(let error):
Data1.mainQueue.async {
closure(nil, error)
}
case .success(let data):
Data1.mainQueue.async {
closure((data as? [String: Any]) ?? [:], nil)
}
}
}
}
class func searchRequest(term: String, closure: #escaping (_ json: [String: Any]?, _ error: Error?)->()) {
let request = Alamofire.request("https://itunes.apple.com/search?term=\(term.replacingOccurrences(of: " ", with: "+"))")
Data1.make(request: request) { json, error in
closure(json, error)
}
}
}
UIViewController
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
Data1.searchRequest(term: "jack johnson") { json, error in
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
}
}
Sample 2
Return data using delegate
// ....
var data = Data2()
data.delegate = self
data.searchRequest(term: "jack johnson")
// ....
extension ViewController: Data2Delegate {
func searchRequest(response json: [String : Any]?, error: Error?) {
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
}
Full sample 2
Data class
import Alamofire
protocol Data2Delegate: class {
func searchRequest(response json: [String: Any]?, error: Error?)
}
class Data2 {
fileprivate let queue = DispatchQueue(label: "requests.queue", qos: .utility)
fileprivate let mainQueue = DispatchQueue.main
weak var delegate: Data2Delegate?
fileprivate func make(request: DataRequest, closure: #escaping (_ json: [String: Any]?, _ error: Error?)->()) {
request.responseJSON(queue: queue) { response in
// print(response.request ?? "nil") // original URL request
// print(response.response ?? "nil") // HTTP URL response
// print(response.data ?? "nil") // server data
//print(response.result ?? "nil") // result of response serialization
switch response.result {
case .failure(let error):
self.mainQueue.async {
closure(nil, error)
}
case .success(let data):
self.mainQueue.async {
closure((data as? [String: Any]) ?? [:], nil)
}
}
}
}
func searchRequest(term: String) {
let request = Alamofire.request("https://itunes.apple.com/search?term=\(term.replacingOccurrences(of: " ", with: "+"))")
make(request: request) { json, error in
self.delegate?.searchRequest(response: json, error: error)
}
}
}
UIViewController
import UIKit
class ViewController: UIViewController {
private var data = Data2()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
data.delegate = self
data.searchRequest(term: "jack johnson")
}
}
extension ViewController: Data2Delegate {
func searchRequest(response json: [String : Any]?, error: Error?) {
print(error ?? "nil")
print(json ?? "nil")
print("Update views")
}
}
Sample 3
Return data using PromiseKit
_ = data.searchRequest(term: "jack johnson").then { response in
print(response.error ?? "nil")
print(response.json ?? "nil")
print("Update views")
return .void
}
Full sample 3
Data class
import Alamofire
import PromiseKit
class Data3 {
fileprivate let queue = DispatchQueue(label: "requests.queue", qos: .utility)
fileprivate let mainQueue = DispatchQueue.main
fileprivate func make(request: DataRequest) -> Promise<(json:[String: Any]?, error: Error?)> {
return Promise { fulfill, reject in
request.responseJSON(queue: queue) { response in
// print(response.request ?? "nil") // original URL request
// print(response.response ?? "nil") // HTTP URL response
// print(response.data ?? "nil") // server data
//print(response.result ?? "nil") // result of response serialization
switch response.result {
case .failure(let error):
self.mainQueue.async {
fulfill((nil, error))
}
case .success(let data):
self.mainQueue.async {
fulfill(((data as? [String: Any]) ?? [:], nil))
}
}
}
}
}
func searchRequest(term: String) -> Promise<(json:[String: Any]?, error: Error?)> {
let request = Alamofire.request("https://itunes.apple.com/search?term=\(term.replacingOccurrences(of: " ", with: "+"))")
return make(request: request)
}
}
extension AnyPromise {
class var void: AnyPromise {
return AnyPromise(Promise<Void>())
}
}
UIViewController
import UIKit
import PromiseKit
class ViewController: UIViewController {
private var data = Data3()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
_ = data.searchRequest(term: "jack johnson").then { response in
print(response.error ?? "nil")
print(response.json ?? "nil")
print("Update views")
return .void
}
}
}

Answer 5

To parse a json using Swifty JSON, here is how i am doing it.
For #Jenita _Alice4Real
func uploadScans(parameters: [String: AnyObject], completionHandler: (AnyObject?, NSError?) -> ()) {
makePostCall(CommonFunctions().getSaveSKUDataUrl(), parameters: parameters,completionHandler: completionHandler)
}
func makePostCall(url: String, parameters: [String: AnyObject], completionHandler: (AnyObject?, NSError?) -> ()) {
Alamofire.request(.POST, url, parameters: parameters)
.responseJSON { response in
switch response.result {
case .Success(let value):
completionHandler(value, nil)
case .Failure(let error):
completionHandler(nil, error)
}
}
}
uploadScans(params) { responseObject, error in
let json = JSON(responseObject!)
}