Wait for multiple Alamofire Requests to finish - ios

Question

I have a below function in my network class which do the Alamofire Request process. I'm calling this function in my model class and when Alamofire finishes the request it calls delegate function which notify model class. My problem is that I'm calling this Alamofire function multiple times and both should finish before notifying model class. Now I handle it with very dummy way. As I searched, DispatchGroup can be used but I can't figure it out, how to implement it. Thank you.
Model Class
#objc func refresh_fiks(){
let network = Network()
network.delegate = self
self.teams = [[]]
network.getRequest(req: 1)
network.getRequest(req: 2)
}
Request Function:
func response(){
print(response_json.count)
if(response_json.count == path){
self.delegate?.sendJson(response_json)
}
}
func getRequest(req: Int) {
path = req
let rot = Router(method: .get, path: req, parameters: nil)
Alamofire.request(rot)
.response { response in
print(response.request?.url! as Any)
// check for errors
guard response.error == nil else {
// got an error in getting the data, need to handle it
print(response.error!)
let errorJson: JSON = [ "Error" : "Can't get the data!"]
self.response_json.append(errorJson)
self.response()
return
}
// make sure we got some JSON since that's what we expect
guard (response.data?.base64EncodedString()) != nil else {
print("Error: \(String(describing: response.error))")
let errorJson: JSON = [ "Error" : "Can't get the data!"]
self.response_json.append(errorJson)
self.response()
return
}
guard response.response?.statusCode == 200 else{
let errorJson: JSON = [ "Error" : "Can't get the data!"]
self.response_json.append(errorJson)
self.response()
return
}
let json = JSON(data: response.data!)
// get and print the title
if json != nil{
self.response_json.append(json)
self.response()
} else {
let errorJson: JSON = [ "Error" : "Can't get the data!"]
self.response_json.append(errorJson)
self.response()
return
}
}
}

Answer 1

I've made few changes in your code:
Network class:
func response(array: [JSON]){
print(array.count)
if(array.count == path){
self.delegate?.sendJson(array)
}
}
func getMultipleRequests(_ requests: [Int]) {
DispatchQueue.global(qos: .background).async {
let group = DispatchGroup()
var array: [JSON] = []
for request in requests {
group.enter()
self.getRequest(req: request, completion: { (json) in
array.append(json)
group.leave()
})
}
group.wait()
//this line below won't be called until all entries will leave the group
self.response(array: array)
}
}
func getRequest(req: Int, completion: #escaping (_ json: JSON) -> Void) {
path = req
let rot = Router(method: .get, path: req, parameters: nil)
Alamofire.request(rot)
.response { response in
print(response.request?.url! as Any)
// check for errors
guard response.error == nil else {
// got an error in getting the data, need to handle it
print(response.error!)
let errorJson: JSON = [ "Error" : "Can't get the data!"]
completion(errorJson)
return
}
// make sure we got some JSON since that's what we expect
guard (response.data?.base64EncodedString()) != nil else {
print("Error: \(String(describing: response.error))")
let errorJson: JSON = [ "Error" : "Can't get the data!"]
completion(errorJson)
return
}
guard response.response?.statusCode == 200 else{
let errorJson: JSON = [ "Error" : "Can't get the data!"]
completion(errorJson)
return
}
let json = JSON(data: response.data!)
// get and print the title
if json != nil{
completion(json)
} else {
let errorJson: JSON = [ "Error" : "Can't get the data!"]
completion(errorJson)
return
}
}
}
So the getRequest function now have a completion block that will return a json result off each request and the function getMultipleRequests that will receive a bunch of requests from anyone
This how you can use it
Your class, that calls refresh_fiks:
#objc func refresh_fiks(){
let network = Network()
network.delegate = self
self.teams = [[]]
network.getMultipleRequests([1,2])
}
Also, instead of using group.wait() you might need to use group.notify, it's better to notify that all entries leaved the group in specified queue, like the main:
group.notify(queue: DispatchQueue.main, execute: {
print("All Done")
self.response(array: array)
})
What to read about the DispatchGroups:
RayWenderlich
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