How can I retry a URLRequest.sharedDataTask until the response is 200?

Question

I am new to Swift and currently stuck on exiting a function containing shared.dataTask once the httpResponse is 200. Any suggestions will be appreciated.

func retryFunc(url: String, requestType: String, requestJsonData: Any, retriesLeft: Int) {
    //Function body
    // declarations
    while self.numberOfretries > 0 {
        let task = URLSession.shared.dataTask(with: request) { data, response, error in
            guard let data = data, error == nil else {
                print(error?.localizedDescription ?? "No data")
                return
            }            
            
            if let httpResponse = response as? HTTPURLResponse {
                print(httpResponse.statusCode)
                if httpResponse.statusCode == 200 {
                    print("Got 200")
                    self.numberOfretries = 0
                    let responseJSON = try? JSONSerialization.jsonObject(with: data, options: [])
                    if let responseJSON = responseJSON as? [String: Any] {
                        print(responseJSON)
                    }
                    return
                }
                if httpResponse.statusCode == 500 {
                    print("Got 500")
                    self.numberOfretries -= 1
                    
                    self.retryFunc(url: url, requestType: <request-type>, requestJsonData: json, retriesLeft: self.numberOfretries)
                }
            }
        }
        task.resume()
    }
}

//calling function from another class
func retryFunc(url: <url>, requestType: <type>, requestJsonData: <jsonData>, retriesLeft: <3>)

I need to exit the function on getting 200 but it still continues to run for the number of retries specified while calling the function.

You never use the retriesLeft parameters. You just use self.numberOfretries. — Ptit Xav, Jan 04 '21 at 17:15
I think this is not a good idea if there is no internet connection it will probably drain the device's battery without a reason. Better to use Reachability and retry it when the flag changes. — Leo Dabus, Jan 05 '21 at 01:21
This is just the snippet. Skipped the declarations part @PtitXav — Ozone17, Jan 05 '21 at 10:43

vadian · Accepted Answer · 2021-01-04T17:40:25.447

Consider that the while loop is outside of the asynchronous task, so a couple of 100 tasks can be created before the counter is being decremented.

A better way is to remove the while loop and check for 0 inside the closure – the retriesLeft parameter makes no sense – for example

func retryFunc(url: String, requestType: String, requestJsonData: Any) {
    //Function body
    // declarations
    
    let task = URLSession.shared.dataTask(with: request) { data, response, error in
                        
        if let error = error {
            print(error.localizedDescription)
            return
        }
                            
        if let httpResponse = response as? HTTPURLResponse {
           print(httpResponse.statusCode)
           if httpResponse.statusCode == 200 {
               print("Got 200")
               do {
                   if let responseJSON = try JSONSerialization.jsonObject(with: data!) as? [String: Any] {
                       print(responseJSON)
                   }
               } catch { print(error) }

           } else if httpResponse.statusCode == 500 {
               print("Got 500")
               self.numberOfretries -= 1
               if self.numberOfretries == 0 { return }
    
               self.retryFunc(url: url, requestType: requestType, requestJsonData: requestJsonData)
           }
       }
    }
    task.resume()
}

Thanks, this was exactly what I was looking for! – Ozone17 Jan 05 '21 at 10:42 — Ozone17, Jan 05 '21 at 10:42

How can I retry a URLRequest.sharedDataTask until the response is 200?

1 Answers1