Question

I have an app that uses Core Data and it gets its ManagedObjectContext by using UIManagedObject. From reading, I see that I am not suppose to save the context directly – rather I should depend on autosaving of UIManagedObject or use saveToURL:… My issue is that I want to validate the data being stored in my entity. I have constraints on the entity that specify that the min length for the string properties is 1. However, I can create a new object, assign its properties empty strings, and save the file. In the completion handler of saveToURL:… it always has a true success value. I then created my own validator for the name property of my entity. I used sample code from the Core Data Programming Guide –

-(BOOL)validateName:(id *)ioValue error:(__autoreleasing NSError **)outError 

{
    if (*ioValue == nil) 

    {
        if (outError != NULL) 

        {
            NSString *errorStr = @"nil error";

            NSDictionary *userInfoDict = [NSDictionary dictionaryWithObject:errorStr

                forKey:NSLocalizedDescriptionKey];

            NSError __autoreleasing *error = [[NSError alloc] initWithDomain:@"domain"

                code:1

                userInfo:userInfoDict];

            *outError = error;

        }

        return NO;

    }

    else if( [*ioValue length] == 0 )

    {

        if (outError != NULL) {

            NSString *errorStr = @"length error";

            NSDictionary *userInfoDict = [NSDictionary dictionaryWithObject:errorStr

                forKey:NSLocalizedDescriptionKey];

            NSError __autoreleasing *error = [[NSError alloc] initWithDomain:@"domain"

                code:1

                userInfo:userInfoDict];

            *outError = error;

        }

        return NO;

    }

    else

    {

        return YES;

    }

}

When this runs, I see that the ioValue has 0 length and that it returns NO, but then my completion handler is never called. Any help would be great.

Is there something I am missing for how to handle saving errors with UIManagedDocument – particularly how to notify the calling code that an error happened while saving its information.

Answer 1

I guess I need to implement handleError:(NSError *)error userInteractionPermitted:(BOOL)userInteractionPermitted in a subclass of the UIManagedDocument. I found that via this article – http://blog.stevex.net/2011/12/uimanageddocument-autosave-troubleshooting/