I have a one to many entity relationship between two entities:
EntityP (Parent) <-->> EntityC (Child)
Attributes and Relationships:
EntityP.title
EntityP.dateTimeStamp
EntityP.PtoC (relationship)
EntityC.title
EntityC.dateTimeStamp
EntityC.CtoP (relationship) // Can be used to get "one" EntityP record
I use fetch results controller to show the results. Here's my implementation of the fetch results controller:
#pragma mark -
#pragma mark Fetched results controller
- (NSFetchedResultsController *)fetchedResultsController {
// Set up the fetched results controller if needed
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
// Create the fetch request for the entity
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Set Entity
NSEntityDescription *entity = [NSEntityDescription entityForName:#"EntityC" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Set Predicate
// (Ignore, we want to get list of all EntityC records)
// Set Sort Descriptors (sort on Parent - for section, and then on Child - for rows)
NSSortDescriptor *sortDescriptorPDate = [[NSSortDescriptor alloc] initWithKey:#"CtoP.dateTimeStamp" ascending:YES];
NSSortDescriptor *sortDescriptorDate = [[NSSortDescriptor alloc] initWithKey:#"dateTimeStamp" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptorPDate, sortDescriptorDate, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
[fetchRequest setFetchBatchSize:20];
// Create and initialize the fetch results controller
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:#"CtoP.title" cacheName:nil];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
// Cleanup memory
[aFetchedResultsController release];
[fetchRequest release];
[sortDescriptorPDate release];
[sortDescriptorDate release];
[sortDescriptors release];
NSError *error = nil;
if (![fetchedResultsController performFetch:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
*/
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return fetchedResultsController;
}
Now, for example, if i have following data in the persistence store:
EntityP.dateTimeStamp EntityP.title EntityC.dateTimeStamp EntityC.title
Today B Today d
Yesterday A Yesterday a
Today B Yesterday c
Yesterday A Today b
Note: Yesterday and Today is in NSDate format.
Then i should get the sections and rows in following order (exactly):
A
a
b
B
c
d
But, the sort is not working like this. I'm getting the rows in correct order, but the sections are not ordered! I hope sortDescriptorPDate is doing his job. What am i missing? Thanking in anticipation.
Not sure I understand your setup but...
By default the section titles are the capitalized first letter of the section name. If you want a custom sections such as ones based on dates, you will need to subclass NSFetchedResultsController and override the various sectionIndex... methods to return the correct sections, section indexes and section titles.
This seems to be working now! I'm not sure what changed! – Mustafa Sep 6 '10 at 4:03
Related
I have Core Data with +2 millions of rows and i want to search for two specific fields: name & phone (for example). I insert scopes for each field in the Search Bar. Everything go fine if I haven't large data set. That's why I want to search in my core data without load all rows in memory before go search controller. Just need a result when my search text length > 3 or when the Search Button Clicked.
I have just one Table View with Search Bar
I populate when AppDidFinish with Call history plist
When the search bar isActive my App frezes until 2 millions rows loads. I need Avoid this step and move forward to step 4
Enter the search text. Then the result filteredArray has shown in the Table View
...
If have any idea I will appreciated.
Here you have some codes:
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Guia" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:50];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:NO];
NSArray *sortDescriptors = #[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"GuiaCache"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
abort();
}
return _fetchedResultsController;
}
Maybe in this method I need to improve with some Predicate
- (NSFetchRequest *)searchFetchRequest
{
if (_searchFetchRequest != nil) {
return _searchFetchRequest;
}
_searchFetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Guia" inManagedObjectContext:self.managedObjectContext];
[_searchFetchRequest setEntity:entity];
[_searchFetchRequest setFetchBatchSize:50];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:NO];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil];
[_searchFetchRequest setSortDescriptors:sortDescriptors];
return _searchFetchRequest;
}
Finaly the two functions to search in Core Data
- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
{
if ([searchText length] > 3)
[self searchForText:searchText scope:_scopeKeyIndex];
}
- (void)searchForText:(NSString *)searchText scope:(NSUInteger)scopeOption
{
if (self.managedObjectContext)
{
NSString *predicateFormat = #"%K BEGINSWITH[cd] %#";
NSString *searchAttribute = #"telephone";
if (scopeOption == 1)
{
searchAttribute = #"name";
}
NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateFormat, searchAttribute, searchText];
[self.searchFetchRequest setPredicate:predicate];
NSError *error = nil;
_filteredList = [self.managedObjectContext executeFetchRequest:self.searchFetchRequest error:&error];
}
}
If you need some other piece of code, just comment.
First, run Instruments against your application, specifically Time Profiler. Where does it say the time is being spent?
Do you have a predicate in your search? What does the predicate look like? You need to show some code for people to help.
Doing a fetch against against 2 million records will take a bit of time but I suspect it is not loading 2 million rows into memory as that would most likely cause memory problems as well as speed problems.
Post the results from Time Profiler and lets see where the time is being spent.
Update
First your predicate is very expensive. BEGINSWITH should be avoided if at all possible. Making it both case and diacritic insensitive increases that cost dramatically.
Did you run Instruments against your code? Did you run the time profiler? Without running that you are just guessing. You NEED to run the time profiler and at least show the results if not link to the entire profile.
First question here and I've tried a bunch of stuff and can't figure it out.
Core Data with 2 entities with to-many relationship both ways
A<<---->>B
A entity has name as an attribute, and a relationship Bs
First Controller lists all A entities and i have a second controller to add A entities and I want to have it save a default B in its relationship.
In the prepare for segue I have this code:
if ([[segue identifier] isEqualToString:#"addAEntitySegue"]) {
AddAEntityViewController *addAEntityViewController = [segue destinationViewController];
addAEntityViewController.delegate = self;
addAEntityViewController.managedObjectContext = self.managedObjectContext;
NSManagedObjectContext *addingContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
self.addingManagedObjectContext = addingContext;
[addingManagedObjectContext setPersistentStoreCoordinator:[[fetchedResultsController managedObjectContext] persistentStoreCoordinator]];
addAEntityViewController.A = [NSEntityDescription insertNewObjectForEntityForName:#"A" inManagedObjectContext:addingContext];
UIBarButtonItem *saveButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSave
target:addAEntityViewController
action:#selector(save:)];
addAEntityViewController.navigationItem.rightBarButtonItem = saveButton;
}
In addAEntityViewController i have this to save
-(IBAction)save:(id)sender
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"B" inManagedObjectContext:self.managedObjectContext];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"name == %#",[defaults objectForKey:#"BDefault"]];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:predicate];
//Set the batch size to a suitable number
[fetchRequest setFetchBatchSize:20];
NSError *error;
self.A.name = textFieldVal;
[self.A addBObject:[[self.managedObjectContext executeFetchRequest:fetchRequest error:&error] objectAtIndex:0]];
NSLog(#"A = %#", self.A.Bs);
[self.delegate addAEntityViewController:self didFinishWithSave:YES];
}
In the addAEntityViewController everything saves correctly even the NSLog(#"A = %#", self.A.Bs); statement shows the B. But when the delegate saves in the First Controller (AEntityViewController) it only saves the A.name but not the relationship A.Bs, I can't figure out what's wrong.
Here's the delegate method:
-(void) addAEntityViewController:self didFinishWithSave:YES{
if (save) {
NSLog(#"saveworkouts");
NSError *error;
if (![addingManagedObjectContext save:&error]) {
// Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
}
// release the adding managed object context
self.addingManagedObjectContext = nil;
}
Like I said it saves the A entity but not the relationship to B even though the relationship to B saved correctly in the addAEntityViewController (the second View). An NSLOg of A.Bs is null.
First I believe that this line:
addAEntityViewController = self.managedObjectContext;
should be:
addAEntityViewController.managedObjectContext = self.managedObjectContext;
but that would also be wrong.
it should be getting the addingContext you created afterwards:
addAEntityViewController.managedObjectContext = addingContext;
I'm a bit surprised that your app didn't crash, as you are mixing managed objects from 2 different contexts.
I have been looking over this issue since a week and haven't got any solution, so I thought to make the question more generalized, may be it will help the users to look into it and give me a solution.
Scenario:
I have an expense tracking iOS Application and I have a view controller called "DashBoardViewController" (table view controller - with FRC) which would basically categorize my expenses/incomes for a given week, a month, or year and display it as the section header title for example : (Oct 1- Oct 7, 2012) and it shows expenses/incomes ROWS and related stuff according to that particular week or month or year.
My Question:
What I want to accomplish is :
Show Distinct Results based on "Category" attribute of "Money" entity and calculate "Sum" based on the attribute.
But, my view controller called "dashboard view controller" is filled with NSFetchedResultsController with section name key path as "type" that can be an expense or an income. In order to get Distinct results, I shall use Result type as NSDictionaryResultsType in my fetch request which will give me unique results but FRC fails, it doesn't work with that. So, how will I get my section names then? I have posted the code below.
EDIT - BASED ON MARTIN'S SUGGESTION
- (void)userDidSelectStartDate:(NSDate *)startDate andEndDate:(NSDate *)endDate
{
AppDelegate * applicationDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
NSManagedObjectContext * context = [applicationDelegate managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Money" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
NSPredicate *predicateDate = [NSPredicate predicateWithFormat:#"(date >= %#) AND (date <= %#)", startDate, endDate];
[fetchRequest setPredicate:predicateDate];
// Edit the sort key as appropriate.
typeSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"type" ascending:YES];
dateSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"date" ascending:YES];
if(self.choiceSegmentedControl.selectedIndex == 0)
{
choiceSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"cat" ascending:NO];
}
if(self.choiceSegmentedControl.selectedIndex == 1)
{
choiceSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"vendor" ascending:NO];
}
if(self.choiceSegmentedControl.selectedIndex == 2)
{
choiceSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"paidBy" ascending:NO];
}
NSArray * descriptors = [NSArray arrayWithObjects:typeSortDescriptor, dateSortDescriptor,choiceSortDescriptor, nil];
[fetchRequest setSortDescriptors:descriptors];
[fetchRequest setIncludesSubentities:YES];
NSError * anyError = nil;
NSArray *propertiesToFetch = [[NSArray alloc] initWithObjects:
[entity.propertiesByName objectForKey:#"cat"],
nil];
[fetchRequest setReturnsDistinctResults:YES];
[fetchRequest setResultType:NSDictionaryResultType];
[fetchRequest setPropertiesToFetch:propertiesToFetch];
NSArray * objects = [context executeFetchRequest:fetchRequest error:&anyError];
for (NSDictionary *d in objects)
{
NSLog(#"NSDictionary = %#", d);
}
NSSet *uniqueSet = [NSSet setWithArray:[objects valueForKey:#"cat"]];
uniqueArray = [NSMutableArray arrayWithArray:[uniqueSet allObjects]];
self.categoryArray = uniqueArray;
if(_fetchedResultsController)
{
[_fetchedResultsController release]; _fetchedResultsController = nil;
}
_fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:#"type" cacheName:nil];
//self.fetchedResultsController.delegate = self; in order to stop "change tracking"
if(![_fetchedResultsController performFetch:&anyError])
{
NSLog(#"error fetching:%#", anyError);
}
[fetchRequest release];
//Finally you tell the tableView to reload it's data, it will then ask your NEW FRC for the new data
[self.dashBoardTblView reloadData];
self.startDate = startDate;
self.endDate = endDate;
}
With this code, SECTION NAME KEY PATH is not working and it's complaining that the object will be placed in unnamed section.
A fetched results controller does not support change tracking (i.e. the FRC delegate is set) in combination with a fetch request with NSDictionaryResultType.
The reason is documented with the setIncludesPendingChanges: function:
Special Considerations
A value of YES is not supported in conjunction
with the result type NSDictionaryResultType, including calculation of
aggregate results (such as max and min). For dictionaries, the array
returned from the fetch reflects the current state in the persistent
store, and does not take into account any pending changes, insertions,
or deletions in the context.
Change tracking of the FRC implies includesPendingChanges = YES for the fetch request, and that does not work with NSDictionaryResultType.
One workaround could be to use a FRC without change tracking, so you do not set the FRC delegate. But that means that to update your table view, you have to
save the managed object context, and
call performFetch on the FRC and reloadData on the table view.
Another workaround could be to use the FRC to fetch all sections and rows without the sum aggregation, and use the results to compute new table rows with the aggregation in memory (e.g. in controllerDidChangeContent).
UPDATE: (From the discussion) Another important point is that if you use a fetch request with NSDictionaryResultType, then the sectionNameKeyPath of the fetched results controller must be included in the propertiesToFetch of the fetch request.
I am using multithreading while loading data from the database.
I am doing the following
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
^{
// Get data
NSDate *pastDate = [CommonHelper getSelectedDateYearBackComponents:[NSDate date]];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"users == %# && startDate >= %#", objUser,pastDate];
NSMutableArray *fetchArray = [DataAccess searchObjectsInUserContext:#"userIngo" :predicate :#"startDate" :NO];
if ([fetchArray count] > 0)
{
dispatch_async(dispatch_get_main_queue(),
^{
// Reload table
[self.tableView reloadData]; });
}
else
{
dispatch_async(dispatch_get_main_queue(),
^{ // calling Webservice
});
}
});
where users is the entity from which I am trying to fetch data and objUser is the user object for whom I am retrieving data from the users entity
and my searchObjectsInUserContext code is like this
+(NSMutableArray *) searchObjectsInLabContext: (NSString*) entityName : (NSPredicate *) predicate : (NSString*) sortKey : (BOOL) sortAscending
{
i3EAppDelegate *appDelegate = (i3EAppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];
[context setUndoManager:nil];
[context setPersistentStoreCoordinator:[appDelegate persistentStoreCoordinator]];
// Register context with the notification center
NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self selector:#selector(mergeChanges:) name:NSManagedObjectContextDidSaveNotification object:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:context];
[request setEntity:entity];
[request setFetchBatchSize:10];
[request setReturnsObjectsAsFaults:NO];
// If a predicate was passed, pass it to the query
if(predicate != nil)
{
[request setPredicate:predicate];
}
// If a sort key was passed, use it for sorting.
if(sortKey != nil)
{
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey ascending:sortAscending];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptors release];
[sortDescriptor release];
}
NSError *error;
NSMutableArray *mutableFetchResults = [[context executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
// NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
[request release];
appDelegate = nil;
return [mutableFetchResults autorelease];
}
So in my searchObjectInUserContext I use multiple managedObjectContext so that it does not create problems for me while multithreading as explained by Fred McCann in his blog post.
However, my problem is at NSMutableArray *mutableFetchResults in my searchObjectsInUserContext because it returns 0 at times even though there is data in the database.
Can someone help me with what I am doing wrong?
You are leaking the context you create; you never release it.
There is no need to register as an observer because you are never saving with that context.
Why are you making a mutable copy of the context? That rarely serves any useful purpose.
How do you know there is data in the database?
Is this method being run on a background thread?
Update
There is nothing wrong with your fetch so I suspect the issue might be one of timing. Is this fetch being run before another thread saves? That would explain the behavior you are seeing.
Also, why are you running this on a background thread? Are you seeing a performance issue that requires a background search like this?
Update 2
First, I still question the need for the background fetching. That is normally reserved for when you have performance issues as fetching is very fast.
Second, you fetch on a background queue but then you don't do anything with the data you fetched. You do not hand it off to the table (which would be bad anyway) you just fetch and throw it away.
If you are fetching just to count then don't fetch, do a -[NSManagedObjectContext -countForFetchRequest: error:]. It will be even faster and removes the need for the background queue call.
If you are expecting to do something with the results you have an issue. Instances of NSManagedObject cannot cross a thread/queue boundary. So fetching on the background queue does very little for the UI. You need to fetch those objects on the main queue/main thread. If you don't you will crash because Core Data does not allow it.
In the end, your background queues are doing you more harm than good and they are not solving the problem you are trying to solve.
I fetch data from a Core Data-base and present them in a UITableView. I use a NSFetchedResultController to fetch the data. I want the user to be able to search in the database, and to do that I use a NSPredicate.
The data is presented in the UITableView and everything works well until I set the NSPredicate to the NSFetchedResultController.
I use this in the ViewDidLoad method:
self.fetchedResultsController = nil;
fetchedResultsController_ = nil;
NSError *error = nil;
if (![[self fetchedResultsController] performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1);
}
and when the user has entered a text from the UITextField, that text will go to the new NSPredicate.
This is done when the search starts:
NSPredicate *pred = nil;
pred = [NSPredicate predicateWithFormat:#"(Designation BEGINSWITH '22')"];
[fetchedResultsController_.fetchRequest setPredicate:pred];
NSError *error = nil;
if (![[self fetchedResultsController] performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1);
}
[tView reloadData];
Right now I use #"(Designation BEGINSWITH '22')" for testing only.
This is my NSFetchedResultsController:
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController_ != nil) {
return fetchedResultsController_;
}
/*
Set up the fetched results controller.
*/
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Product" inManagedObjectContext:importContext];//self.managedObjectContext
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:20];
// Edit the sort key as appropriate.
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"Designation" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Edit the section name key path and cache name if appropriate.
// nil for section name key path means "no sections".
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:importContext sectionNameKeyPath:nil cacheName:#"Root"]; //self.managedObjectContext
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
[sortDescriptor release];
[sortDescriptors release];
return fetchedResultsController_;
}
The problem is that the fetched data stays the same, no matter how or if I set a predicate. If I would set a predicate in the viewDidLoad it would work, but then I wouldn't be able to get new results if I'd tried that again. I use an "importContext" for a batch-import of my CoreData.
Any ideas?
Thanks in advance!
UPDATE:
Ok, here is what I found out. I have an importContext where I make a batch-import. And for the fetchController I use self.managedObjectContext. That's why it doesn't work, so I have to make self.managedObjectContext have the same stuff as my importContext somehow...
You're using a cache (#"Root")… Try setting it to nil, this could prevent crashes. You should not cache FetchedResultsControllers meant to be Predicated.
Even better than setting the cache to nil is giving it a unique name. After posting this question
iPhone - Cache name for NSFetchedResultsController
I added a function to generate UUIDs as my cache names.