As stated in the title.
I am running the following code.
Each time I perform an API call, I create a new instance of URLSession and use a background-configured session to allow background API calls.
`
Code being executed:
import Foundation
// Model definitions
struct RandomUserResponse: Codable {
let results: [RandomUser]
}
struct RandomUser: Codable {
let name: Name
let email: String
}
struct Name: Codable {
let first: String
let last: String
}
// Fetcher class
class RandomUserFetcher: NSObject, URLSessionDataDelegate {
private var receivedData = Data()
private var completion: ((RandomUser?) -> Void)?
private var session: URLSession!
func fetchRandomUserInBackground(completion: @escaping (RandomUser?) -> Void) {
self.completion = completion
let configuration = URLSessionConfiguration.background(withIdentifier: "com.example.randomuser.bg")
session = URLSession(configuration: configuration, delegate: self, delegateQueue: nil)
let url = URL(string: "https://randomuser.me/api/" )!
let task = session.dataTask(with: url)
task.resume()
}
// Data received
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
receivedData.append(data)
}
// Completion
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
defer { self.session.finishTasksAndInvalidate() }
guard error == nil else {
print("Error: \(error!)")
completion?(nil)
return
}
do {
let response = try JSONDecoder().decode(RandomUserResponse.self, from: receivedData)
completion?(response.results.first)
} catch {
print("Decoding error: \(error)")
completion?(nil)
}
}
}`
Called in viewDidLoad, etc.:
let fetcher = RandomUserFetcher()
fetcher.fetchRandomUserInBackground { user in
if let user = user {
print("Name: \(user.name.first) \(user.name.last), Email: \(user.email)")
} else {
print("Failed to fetch random user.")
}
}
In Instruments' Network instrument, I focus on my app's process, use 'Command + 3', and switch to 'List: URLSessionTasks'.
Even though didCompleteWithError is called and the API call fully completes, the Duration keeps increasing, and the Success column remains '-' (neither 'Yes' nor 'No').
For non-background URLSessions, the session shows up as 'unnamed session', but for background URLSessions, it appears as 'unnamed background session 1 (XXXXXX-XXXXXX-XXXXX)'.
Does this mean the session is not actually being completed?
I've checked Debug Memory Graph and confirmed there is no NSURLSession memory leak, but is it possible that the app is somehow still retaining session information internally?
I also suspect that Instruments may not be able to fully track background URLSession tasks.