Error Handling When Saving a CKRecord - ios

Question

I am looking for an example of proper error handling when saving a CKRecord. According to the Apple docs I should "Use the information in the error object to determine whether a problem has a workaround."
I understand that the error object has a userInfo dictionary, but how do I figure out what the keys are for the dictionary and how to handle the errors?
The following example illustrates how I'm currently saving a CKRecord:
CKRecord *record = [[CKRecord alloc] initWithRecordType:#"MyRecordType"];
[record setValue:[NSNumber numberWithInt:99] forKey:#"myInt"];
[db saveRecord:record completionHandler:^(CKRecord *savedPlace, NSError *error) {
// handle errors here
if (savedPlace) {
NSLog(#"save successful");
}else{
NSLog(#"save unsuccessful");
}
if (error) {
NSLog(#"Error saving %#", error.localizedDescription);
}
}];
How can I improve this code to provide work arounds for potential saving issues?

Answer 1

In my library EVCloudKitDao I have a separate method that will return a error type based on the error code. Depending on that type you can decide what to do. Here is that method:
public enum HandleCloudKitErrorAs {
case Success,
Retry(afterSeconds:Double),
RecoverableError,
Fail
}
public static func handleCloudKitErrorAs(error:NSError?, retryAttempt:Double = 1) -> HandleCloudKitErrorAs {
if error == nil {
return .Success
}
let errorCode:CKErrorCode = CKErrorCode(rawValue: error!.code)!
switch errorCode {
case .NetworkUnavailable, .NetworkFailure, .ServiceUnavailable, .RequestRateLimited, .ZoneBusy, .ResultsTruncated:
// Use an exponential retry delay which maxes out at half an hour.
var seconds = Double(pow(2, Double(retryAttempt)))
if seconds > 1800 {
seconds = 1800
}
// Or if there is a retry delay specified in the error, then use that.
if let userInfo = error?.userInfo {
if let retry = userInfo[CKErrorRetryAfterKey] as? NSNumber {
seconds = Double(retry)
}
}
NSLog("Debug: Should retry in \(seconds) seconds. \(error)")
return .Retry(afterSeconds: seconds)
case .UnknownItem, .InvalidArguments, .IncompatibleVersion, .BadContainer, .MissingEntitlement, .PermissionFailure, .BadDatabase, .AssetFileNotFound, .OperationCancelled, .NotAuthenticated, .AssetFileModified, .BatchRequestFailed, .ZoneNotFound, .UserDeletedZone, .InternalError, .ServerRejectedRequest, .ConstraintViolation:
NSLog("Error: \(error)")
return .Fail;
case .QuotaExceeded, .LimitExceeded:
NSLog("Warning: \(error)")
return .Fail;
case .ChangeTokenExpired, .ServerRecordChanged:
NSLog("Info: \(error)")
return .RecoverableError
default:
NSLog("Error: \(error)") //New error introduced in iOS...?
return .Fail;
}
}
Inside the callback of a CloudKit method you can then use this function like this:
func loadContacts(retryCount:Double = 1) {
// Look who of our contact is also using this app.
EVCloudKitDao.publicDB.allContactsUserInfo({ users in
EVLog("AllContactUserInfo count = \(users.count)");
Async.main{
self.contacts = users
self.tableView.reloadData()
}
}, errorHandler: { error in
switch EVCloudKitDao.handleCloudKitErrorAs(error, retryAttempt: retryCount) {
case .Retry(let timeToWait):
Async.background(after: timeToWait) {
self.loadContacts(retryCount + 1)
}
case .Fail:
Helper.showError("Something went wrong: \(error.localizedDescription)")
default: // For here there is no need to handle the .Success, .Fail and .RecoverableError
break
}
})
}
In my the case above I use a separate error callback handler. You can also call it directly form within a CloudKit method callback. Just first check if there is an error.

Answer 2

Here is an implementation in which I handle the common error of CKErrorNetworkFailure by retrying to save after the recommended retry after time interval which is stored in the userInfo dictionary.
-(void)saveRecord:(CKRecord*)record toDatabase:(CKDatabase*)database{
[database saveRecord:record completionHandler:^(CKRecord *record, NSError *error) {
if (error==nil) {
NSLog(#"The save was successful");
//Do something
}else{
NSLog(#"Error saving with localizedDescription: %#", error.localizedDescription);
NSLog(#"CKErrorCode = %lu", [error code]);
if ([error code]==CKErrorNetworkFailure) {
double retryAfterValue = [[error.userInfo valueForKey:CKErrorRetryAfterKey] doubleValue];
NSLog(#"Error code network unavailable retrying after %f", retryAfterValue);
NSTimer *timer = [NSTimer timerWithTimeInterval:retryAfterValue target:self selector:#selector(testOutCloudKit) userInfo:nil repeats:NO];
[timer fire];
}
}
}];
}

Answer 3

In Swift 3, I handle my CloudKit errors this way:
privateDB.perform(myQuery, inZoneWith: nil) {records, error in
if error != nil {
print (error?.localizedDescription)
if error?._code == CKError.notAuthenticated.rawValue {
// Solve problems here...
}
Note that the CKError.notAuthenticated is selected from the list presented by code completion after writing CKError.
Hope this helps!