What's the best way to make an NSManagedObject attribute Unique?
For example, should willSave or validateForInsert: or validateForUpdate: managed object methods be used to check if the value entered in attributeUnique is Unique? And, how exactly?
I ended up writing an NSManagedObject category method, and using the NSManagedObject's validation method:
- (BOOL)isValueUniqueForKey:(NSString *)key {
NSEntityDescription *entity = [NSEntityDescription entityForName:[self.entity name]
inManagedObjectContext:self.managedObjectContext];
id value = [self valueForKey:key];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"%# = %#", key, value];
fetchRequest.predicate = predicate;
NSError *error = nil;
NSUInteger count = [self.managedObjectContext countForFetchRequest:fetchRequest
error:&error];
if (count > 1) {
return NO;
}
return YES;
}
Related
I have 1-many relationship and I am successfully putting data into it. The problem is that I am not able to fetch it out via the relationship attribute.
My ADD Code:
NSManagedObjectContext *context = [[CBICoreDataController sharedInstance] masterManagedObjectContext];
NSManagedObject *orders = [NSEntityDescription
insertNewObjectForEntityForName:#"UnsyncedOrders"
inManagedObjectContext:context];
[orders setValue:[dictionary valueForKey:#"specialInstructions"] forKey:#"specialInstructions"];
[orders setValue:[dictionary valueForKey:#"poNumber"] forKey:#"poNumber"];
[orders setValue:[dictionary valueForKey:#"specialInstructions"] forKey:#"specialInstructions"];
[orders setValue:[dictionary valueForKey:#"deliveryDate"] forKey:#"deliveryDate"];
[orders setValue:[dictionary valueForKey:#"account"] forKey:#"account"];
NSMutableSet *muteSet=[orders mutableSetValueForKey:#"items"];
for (NSDictionary *dict in [dictionary valueForKey:#"items"]) {
NSManagedObject *items = [NSEntityDescription
insertNewObjectForEntityForName:#"UnsyncedOrderItems"
inManagedObjectContext:context];
[items setValue:[dict valueForKey:#"arraykey"] forKey:#"arrayKey"];
//Other Sets Here
[muteSet addObject:items];
}
[orders setValue:muteSet forKey:#"items"];
NSError *error;
if (![context save:&error]) {
NSLog(#"Error saving in writeToMenuCostingDetailsTable: %#", [error localizedDescription]);
}
What I have for the fetch now but it does not work:
NSFetchRequest * fetchRequest = [[NSFetchRequest alloc] init];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"arrayKey" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
NSEntityDescription *parent = [NSEntityDescription entityForName:#"UnsyncedOrders"
inManagedObjectContext:context];
NSEntityDescription *child = [NSEntityDescription entityForName:#"UnsyncedOrderItems"
inManagedObjectContext:context];
[fetchRequest setEntity:child];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"orders == %#", parent];
[fetchRequest setPredicate:predicate];
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:nil cacheName:nil];
NSError *error;
[aFetchedResultsController performFetch:&error];
NSArray *fetchedObjects = [aFetchedResultsController fetchedObjects];
Your orders relationship relates to a specific instance of UnsyncedOrders. However when you try to perform a fetch, you do this:
NSEntityDescription *parent = [NSEntityDescription entityForName:#"UnsyncedOrders"
inManagedObjectContext:context];
[...]
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"orders == %#", parent];
[fetchRequest setPredicate:predicate];
You're trying to fetch instances where the orders relationship points to the UnsyncedOrders entity itself, not those that relate to a specific instance of UnsyncedOrders. That's always going to fail. In fact there's a good chance that if you were checking the result of performFetch: that it's returning NO and providing you with some sort of error describing the problem.
If you want to fetch the UnsyncedOrderItems that relate to a specific instance of UnsyncedOrders, you need to use a predicate that refers to a specific instance. However, if you already have that instance, you don't need to fetch-- just ask the UnsyncedOrders instance for the value of its items relationship.
This is the solution that I ended up using:
NSManagedObjectContext *context = [[CBICoreDataController sharedInstance] masterManagedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"UnsyncedOrders"
inManagedObjectContext:context];
NSError *error = nil;
[fetchRequest setEntity:entity];
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
for (UnsyncedOrders *info in fetchedObjects) {
[mutableArray addObject:info.items];
}
I've my entity in CoreData named as myentity and an attribute named as myuniqueid and I want to run an SQL query as follows:
Select * from myentity where myuniqueid == 1000
How can I get my specified rows where it matches as in SQL query? such that I want to filter all rows where myuniqueid is 1000.
My Code:
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSManagedObjectContext *context = [self managedObjectContext];
if (context == nil) {}
else {
NSEntityDescription *entity = [NSEntityDescription entityForName:#"myentity" inManagedObjectContext:context];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"myuniqueid == 1000"];
[fetchRequest setPredicate:predicate];
[fetchRequest setEntity:entity];
NSArray *items = [context executeFetchRequest:fetchRequest error:nil];
for (int i=0; i<4; i++) {
NSManagedObject *mo = [items objectAtIndex:i]; // assuming that array is not empty
id value = [mo valueForKey:#"myuniqueid"];
NSLog(#"SENDER: %#",value);
}
}
Im getting error: 'Unable to generate SQL for predicate (myuniqueid == 1000) (problem on RHS)'
Try this predicate :
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:#"myentity"];
fetchRequest.predicate = [NSPredicate predicateWithFormat:#"myuniqueid == %#", #(1000)];
NSArray *items = [[self managedObjectContext] executeFetchRequest:request error:nil];
I save to core data and load all messages with code below, but how can I load only messages for 2 users, for self user and for destination user, I want base it on user JID.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSManagedObjectContext *context = [[self appDelegate].xmppMessageArchivingCoreDataStorage mainThreadManagedObjectContext];
NSEntityDescription *messageEntity = [NSEntityDescription entityForName:#"XMPPMessageArchiving_Message_CoreDataObject" inManagedObjectContext:context];
fetchRequest.entity = messageEntity;
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"timestamp" ascending:YES];
fetchRequest.sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSError *error = nil;
NSArray *results = [context executeFetchRequest:fetchRequest error:&error];
//Now you get the NSArray with element type of "XMPPMessageArchiving_Message_CoreDataObject"
assuming your message objects have a from relationshit to a User entity.
As simple as adding (before executing the request):
fetchRequest.predicate = [NSPredicate predicateWithFormat:#"from = %# OR from = %#",selfUser,otherUser];
Where selfUser and otherUser are User core data managed objects or managed object IDs of users.
if you use a field identifier (highly not recomended):
fetchRequest.predicate = [NSPredicate predicateWithFormat:#"bareJID.bare = %# OR bareJID.bare = %#",selfUser.jid,otherUser.jid];
You might want to read THIS
I have used following method and it worked correctly :)
-(void)checkForPastMessageAndDisplayIt
{
NSString *strmyid = #"user1#domain";
NSString *strBuddy = #"user2#domain";
NSManagedObjectContext *moc = [[self appDelegate] managedObjectContext_message_achiving];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"XMPPMessageArchiving_Message_CoreDataObject"
inManagedObjectContext:moc];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
fetchRequest.predicate = [NSPredicate predicateWithFormat:#"bareJidStr = %# OR bareJidStr = %#", strmyid, strBuddy];
[fetchRequest setEntity:entity];
NSError *error;
NSArray *messagesArray = [moc executeFetchRequest:fetchRequest error:&error];
[messagesArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
id messageObject = [messagesArray objectAtIndex:idx];
if ([messageObject isKindOfClass:[XMPPMessageArchiving_Message_CoreDataObject class]]) {
XMPPMessageArchiving_Message_CoreDataObject *currentMessageCoreDataObject = (XMPPMessageArchiving_Message_CoreDataObject*)messageObject;
XMPPMessage *message = currentMessageCoreDataObject.message;
if (message!=nil) {
[messages addObject:message];
}
}
}];
}
You can use like that
-(void)testMessageArchiving {
NSString *strmyid = #"myid";
NSString *strBuddy ="toid";
NSLog(#"my id and buddy is is %# and %#",strmyid,strBuddy);
XMPPMessageArchivingCoreDataStorage *storage = [XMPPMessageArchivingCoreDataStorage sharedInstance];
NSManagedObjectContext *moc = [storage mainThreadManagedObjectContext];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:#"XMPPMessageArchiving_Message_CoreDataObject"
inManagedObjectContext:moc];
NSFetchRequest *request = [[NSFetchRequest alloc]init];
request.predicate = [NSPredicate predicateWithFormat:#"bareJidStr = %# OR bareJidStr = %#", strmyid, strBuddy];
NSError *error;
NSArray *messages = [moc executeFetchRequest:request error:&error];
// NSLog(#"the history of messages is %#",messages);
[self print:[[NSMutableArray alloc]initWithArray:messages]];
I have a core data model that has a one to many relationship, there is a category, and it can contain many subcategories.
Category <---->> Subcategory
I am trying to perform a fetch that checks if a particular Category contains a Subcategory with a particular name. Let's say I have two categories below, I want to fetch to see if there are any subcategories name "Apple" in the Category named "Fruits".
Vetegables
- Carrot
- Lettuce
Fruits
- Apple
- Orange
- Pear
Code:
- (SubCategory *)searchForSubCategoryWithName:(NSString *)subCategory
inCategory:(Category *)category
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"SubCategory" inManagedObjectContext:self.beer.managedObjectContext];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"name == [c] %#", subCategory];
[fetchRequest setPredicate:predicate];
NSError *error;
NSArray *fetchedObjects = [self.beer.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects != nil && fetchedObjects.count > 0) {
return [fetchedObjects objectAtIndex:0];
}
else {
return nil;
}
}
Try looking for category entity which has subcategory you like not the other way around, then return category.subcategory from results. I am not sure how your NSManagedObjects look like but try this:
- (SubCategory *)searchForSubCategoryWithName:(NSString *)subCategory
inCategory:(Category *)category
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Category" inManagedObjectContext:self.beer.managedObjectContext];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"subcategory.name == [c] %# AND name == %#", subCategory, category.name];
[fetchRequest setPredicate:predicate];
NSError *error;
NSArray *fetchedObjects = [self.beer.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects != nil && fetchedObjects.count > 0) {
Category *categoryManagedObject = [fetchedObjects objectAtIndex:0];
return categoryManagedObject.subcategory;
}
else {
return nil;
}
}
...or just add category to your predicate, you should have it in your subcategory managed object definition:
- (SubCategory *)searchForSubCategoryWithName:(NSString *)subCategory
inCategory:(Category *)category
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Category" inManagedObjectContext:self.beer.managedObjectContext];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"name == [c] %# AND category == %#", subCategory, category];
[fetchRequest setPredicate:predicate];
NSError *error;
NSArray *fetchedObjects = [self.beer.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (fetchedObjects != nil && fetchedObjects.count > 0) {
return [fetchedObjects objectAtIndex:0];
}
else {
return nil;
}
}
I have 2 entity, Units and BUnits, the Units entity have a data that will be replaced many time, and the BUnits will be the backup of the Units entity before clearing it's data.
So, I've created a NSManagedObjectContext instance, then I've retrive an instance for each entity by using
NSManagedObjectContext *context = [mainDelegate managedObjectContext];
NSEntityDescription *unitsEntity = [NSEntityDescription entityForName:#"Units" inManagedObjectContext:context];
NSEntityDescription *bUnitsEntity = [NSEntityDescription entityForName:#"BUnits" inManagedObjectContext:context];
but i've didn't managed to copy the Units entity records to the BUnits entity, other than make a loop for each records, but i believe that there is a better solution.
What do you think about this, is there a better solution?
UPDATE:
The solution i've used in case anyone could use it is in my answer, I think there is a better way to do this, i will keep checking for it and i will update the question if i found anything.
Here is what i've used, using looping for each record:
- (void) copyEntities:(NSString *)sourceEntity And:(NSString *)destinationEntity {
NSManagedObjectContext *context = [mainDelegate managedObjectContext];
NSEntityDescription *Units = [NSEntityDescription entityForName:sourceEntity inManagedObjectContext:context];
NSEntityDescription *BUnits = [NSEntityDescription entityForName:destinationEntity inManagedObjectContext:context];
NSFetchRequest *dataRequest = [[NSFetchRequest alloc] init];
[dataRequest setEntity:Units];
NSError *error = nil;
NSArray *dataArray = [context executeFetchRequest:dataRequest error:&error];
for (UnitsClass *unit in dataArray) {
UnitsClass *savedUnits;
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:BUnits];
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(code = %#)", unit.code];
NSPredicate *pred1 = [NSPredicate predicateWithFormat:#"(code2 = %#)", unit.code2];
NSPredicate *compoundPredicate = [NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects:pred, pred1, nil]];
[request setPredicate:compoundPredicate];
NSError *error = nil;
NSArray *objects = [context executeFetchRequest:request error:&error];
//this if to indicate if we inserting to the BUnits or updating it.
if ([objects count] > 0) {
//Found the record, update The info
savedUnits = [objects objectAtIndex:0];
} else {
savedUnits = [NSEntityDescription insertNewObjectForEntityForName:destinationEntity inManagedObjectContext:context];
}
savedUnits.code = unit.code;
/*Add your updated info*/
NSError *errors;
if (![context save:&errors]) {
NSLog(#"Whoops, couldn't save: %#", [errors localizedDescription]);
}
}
NSLog(#"BUnits count = %d",[context countForFetchRequest:[NSFetchRequest fetchRequestWithEntityName:destinationEntity] error:&error]);
}
Based on the given information, there is no better way than looping each unit object and creating the backup object.