Recipes to update database in Core Data - objective-c

Question

I have a method for adding stamp to the card, from QR code reader to web service
my question is,
Here is my code:
- (void)addStamp
{
NSString *url = [_URL stringByAppendingString:#"add-stamp"];
NSString *post = [NSString stringWithFormat:#"userId=%#&code=%#", self.userId, self.code ];
post = [post stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSData *postData = [NSData dataWithBytes:[post UTF8String]
length:[post lengthOfBytesUsingEncoding:NSUTF8StringEncoding]];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL
URLWithString:url] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:600];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:postData];
}
Rightnow I want to update my DB with new method -> if the code is repeated add stamp, if not create add a new card:
-(void)addStampInDB:(int)cardId
{
NSManagedObjectContext* managedObjectContext = [(AppDelegate*) [[UIApplication
sharedApplication] delegate] managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Card"
inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"remote_id = %d", cardId];
[fetchRequest setPredicate:predicate];
[managedObjectContext lock];
NSError *error;
NSArray *fetchedObjects = [managedObjectContext executeFetchRequest:fetchRequest
error:&error];
[managedObjectContext unlock];
Card *d = nil;
if([fetchedObjects count] > 0 ){
d = [fetchedObjects objectAtIndex:0];
cardId++;
} else{
d = [NSEntityDescription insertNewObjectForEntityForName:#"Card"
inManagedObjectContext:managedObjectContext];
}
NSArray *test;
for(NSDictionary *stamp in test)
{
d.remote_id = [NSNumber numberWithInt:[[stamp objectForKey:#"id"] intValue]];
d.stampNumber = [NSNumber numberWithInt:[[stamp objectForKey:#"stampNumber"] intValue]];
d.createdAt = [NSDate dateWithTimeIntervalSince1970:[[stamp objectForKey:#"createdAt"]
intValue]];
[managedObjectContext lock];
NSError *error;
if (![managedObjectContext save:&error])
{
NSLog(#"Whoops, couldn't save: %#", [error localizedDescription]);
NSLog(#"Failed to save to data store: %#", [error localizedDescription]);
NSArray* detailedErrors = [[error userInfo] objectForKey:NSDetailedErrorsKey];
if(detailedErrors != nil && [detailedErrors count] > 0) {
for(NSError* detailedError in detailedErrors) {
NSLog(#" DetailedError: %#", [detailedError userInfo]);
}
} else {
NSLog(#" %#", [error userInfo]);
}
}
[managedObjectContext unlock];
}
}
I don't know if I'm in a right way or not and also how I can test my method?

Answer 1

I'm not very sure about your question but I'll try to give some hints.
First
Card *d = nil;
if([fetchedObjects count] > 0 ){
d = [fetchedObjects objectAtIndex:0];
cardId++;
} else{
d = [NSEntityDescription insertNewObjectForEntityForName:#"Card"
inManagedObjectContext:managedObjectContext];
}
Here you have found an existing card, you use it, else you create a new. Question: what about cardId? Where is it used?
Second
for(NSDictionary *stamp in test)
{
d.remote_id = [NSNumber numberWithInt:[[stamp objectForKey:#"id"] intValue]];
d.stampNumber = [NSNumber numberWithInt:[[stamp objectForKey:#"stampNumber"] intValue]];
d.createdAt = [NSDate dateWithTimeIntervalSince1970:[[stamp objectForKey:#"createdAt"]
intValue]];
// other code here
}
If you loop test, you overwrite the value of your card d each time. Is it right?
Third
for(NSDictionary *stamp in test)
{
// other code here
}
// save here
Move the save out of the for loop. This boost performances in your app. It is not necessary to save each time in your loop. Do it at the end only.
Hope that helps.
P.S. If you want to know something else let me know.