Handling reject with PromiseKit with Swift standard networking? - json

Question

I've got small function that uses native solutions to parse and decode JSON. Everything works fine, except handling errors. I know that when error occurs, I should get JSON with error and message
func fetchCardDetails(withNumber number: Int) -> Promise<CardDetails> {
guard let URL = URL(string: "\(URLProvider.url)/\(APIKeyProvider.apiKey)/\(number)/") else {
fatalError("Could not reformat string to URL!")
}
var request = URLRequest(url: URL)
request.httpMethod = "GET"
let decoder = JSONDecoder()
let session = URLSession.shared
return Promise { fullfill, reject in
let dataTask = session.dataTask(with: request) { data, response, error in
if let data = data,
let json = (try? decoder.decode(CardDetails.self, from: data)) {
fullfill(json)
} else if let error = error {
reject(error)
} else if let response = response {
print(response)
} else if data != nil {
let data = NSError()
reject(data)
} else {
reject(PMKError.invalidCallingConvention)
}
}
dataTask.resume()
}
}
func fetchCardDetails(number: Int) {
_ = cardDetailsService.fetchCardDetails(withNumber: number).then { cardDetails -> Void in
//some actions with cardDetails
}
}
When getting error - nothing crashes but I am getting error Pending Promise deallocated! This is usually a bug. F.A.Q. from PromiseKit didn't help me though.
Should I maybe decode JSON with error and change whole reject closure?

Answer 1

This part of your if statement neither fulfills or rejects.
else if let response = response {
print(response)
}
If you neither fulfill or reject then the promise never resolves and if an unresolved promise is deallocated it prints the warning you are seeing to the console.
Please see the PromiseKit troubleshooting guide for more information.