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iOS NSPredicate not working

P

ppn

macrumors member
Original poster
Oct 31, 2010
36
0
Hey Everyone,

I am trying to create a UITableViewController where one of the functions is to find out how many of each "section" is in my core data. I'm using the NS predicate to set a predicate for my entity as shown below in my countSection method. My sections are A, B, C, D, E and it's only return 1 for A but I have a lot more of each and the other sections are returning 0. I'm noticing if I change my last entry to B then it returns 1 for B. Is there a reason why it's only looking at the last entry instead of the entire database?

Also, when I try to addObject into my NSMutableArray sectionCountNumber, nothing is being added because when I display the "temp", it's showing (null).

At the end of the loop, I'm getting this error: -[NSCFString stringValue]: unrecognized selector sent to instance 0xb298.

Code: 
- (void)countSection {
	for (int i = 0; i<[lessonSection count]; i++) {
		NSFetchRequest *request =[[NSFetchRequest alloc] init];
		if (self.managedObjectContext_ == nil) {
			self.managedObjectContext_ = [(OntarioG1TestAppDelegate *)[[UIApplication sharedApplication] delegate]managedObjectContext];
		}
		NSEntityDescription *entity = [NSEntityDescription entityForName:@"Quiz"
												  inManagedObjectContext:managedObjectContext_];
		[request setEntity:entity];
		NSString *sectionName = [lessonSection objectAtIndex:i];
		NSLog(@"%@", sectionName);
		NSPredicate *predicate = [NSPredicate predicateWithFormat:@"section==%@", sectionName];
		[request setPredicate:predicate];
		NSError *error;
		// the sections are: 
		sectionCountNumber = [managedObjectContext_ countForFetchRequest:request error:&error];
		NSLog(@"%i", sectionCountNumber);
		[sectionCount addObject:[NSNumber numberWithInteger:sectionCountNumber]];
		NSString *temp = [sectionCount objectAtIndex:i];
		NSLog(@"%@", temp);
		[request release];
	}
}

Here's the complete LessonTableView.h code:

Code: 
@protocol LessonTableViewDelegate;

@interface LessonTableView : UITableViewController {
	id <LessonTableViewDelegate> delegate;
	IBOutlet UIImageView *image;
	IBOutlet UILabel *question;
	IBOutlet UILabel *answerA;
	IBOutlet UILabel *answerB;
	IBOutlet UILabel *answerC;
	IBOutlet UILabel *answerD;
	IBOutlet UIButton *showAnswer;
	IBOutlet UIButton *next;
	NSInteger qid;
	NSInteger counter;
	NSInteger sectionCountNumber;
	NSManagedObjectContext *managedObjectContext_;
	NSMutableArray *lessons;
	NSMutableArray *lessonSection;
	NSMutableArray *sectionCount;
	//Quiz *currentLesson;

}

@property (nonatomic, assign) id <LessonTableViewDelegate> delegate;
@property (nonatomic, retain) UIImageView *image;
@property (nonatomic, retain) UILabel *question, *answerA, *answerB, *answerC, *answerD;
@property (nonatomic, retain) UIButton *showerAnswer, *next;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext_;
@property (nonatomic, retain) NSMutableArray *lessons, *lessonSection;
@property (nonatomic, retain) NSMutableArray *sectionCount;
@property (nonatomic, assign) NSInteger qid;
@property (nonatomic, assign) NSInteger counter;
@property (nonatomic, assign) NSInteger sectionCountNumber;

-(void)countSection;

@end

@protocol LessonTableViewDelegate
- (void)lessonTableViewDidFinish:(LessonTableView *)lesson;
@end

Here's my complete LessonTableView.m file:

Code: 
@implementation LessonTableView
@synthesize delegate;
@synthesize image;
@synthesize question, answerA, answerB, answerC, answerD;
@synthesize showerAnswer, next;
@synthesize lessons, lessonSection;
@synthesize sectionCount;
@synthesize managedObjectContext_;
@synthesize qid, counter, sectionCountNumber;

#pragma mark -
#pragma mark View lifecycle


- (void)viewDidLoad {
	lessonSection = [[NSMutableArray alloc] initWithObjects:@"A",@"B",@"C",@"D", @"E", nil];
}

- (void)countSection {
	for (int i = 0; i<[lessonSection count]; i++) {
		NSFetchRequest *request =[[NSFetchRequest alloc] init];
		if (self.managedObjectContext_ == nil) {
			self.managedObjectContext_ = [(OntarioG1TestAppDelegate *)[[UIApplication sharedApplication] delegate]managedObjectContext];
		}
		NSEntityDescription *entity = [NSEntityDescription entityForName:@"Quiz"
												  inManagedObjectContext:managedObjectContext_];
		[request setEntity:entity];
		NSString *sectionName = [lessonSection objectAtIndex:i];
		NSLog(@"%@", sectionName);
		NSPredicate *predicate = [NSPredicate predicateWithFormat:@"section==%@", sectionName];
		[request setPredicate:predicate];
		NSError *error;
		// the sections are: 
		sectionCountNumber = [managedObjectContext_ countForFetchRequest:request error:&error];
		NSLog(@"%i", sectionCountNumber);
		[sectionCount addObject:[NSNumber numberWithInteger:sectionCountNumber]];
		NSString *temp = [sectionCount objectAtIndex:i];
		NSLog(@"%@", temp);
		[request release];
	}
}

/*
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
}
*/
/*
- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
}
*/
/*
- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
}
*/
/*
- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
}
*/
/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/


#pragma mark -
#pragma mark Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
    return [lessonSection count];
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    return [[sectionCount objectAtIndex:section] intValue];
}

- (NSString *)tableView:(UITableView *)tableView
titleForHeaderInSection:(NSInteger)section {
	NSString *temp = [[lessonSection objectAtIndex:section] stringValue];
	NSLog(@"%@", temp);
	return [[lessonSection objectAtIndex:section] stringValue];
}



// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *CellIdentifier = @"Cell";
    
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
    }
    
    // Configure the cell...
    
    return cell;
}


/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
    // Return NO if you do not want the specified item to be editable.
    return YES;
}
*/


/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}
*/


/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
}
*/


/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/


#pragma mark -
#pragma mark Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    // Navigation logic may go here. Create and push another view controller.
	/*
	 <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil];
     // ...
     // Pass the selected object to the new view controller.
	 [self.navigationController pushViewController:detailViewController animated:YES];
	 [detailViewController release];
	 */
}


#pragma mark -
#pragma mark Memory management

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];
    
    // Relinquish ownership any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
    // For example: self.myOutlet = nil;
}


- (void)dealloc {
	[lessons release];
	[image release];
	[question release];
	[answerA release];
	[answerB release];
	[answerC release];
	[answerD release];
	[managedObjectContext_ release];
	[lessonSection release];
	[sectionCount release];
    [super dealloc];
}


@end
 
this is my Quiz Entity in Core Data

Code: 
@property (nonatomic, retain) NSNumber * status;
@property (nonatomic, retain) NSNumber * qid;
@property (nonatomic, retain) NSString * answerD;
@property (nonatomic, retain) NSString * answerC;
@property (nonatomic, retain) NSString * answerB;
@property (nonatomic, retain) NSString * question;
@property (nonatomic, retain) NSString * answerA;
@property (nonatomic, retain) NSString * section;
@property (nonatomic, retain) NSNumber * solution;
@property (nonatomic, retain) NSString * images;
 
I've initialized my section count and it's not returning null anymore but I still can't get my predicate to work. I've modified my countSection method and added a currentLesson as follows:

Code: 
- (Quiz *) currentLesson {
	if (self.counter < 0) {
		return nil;
	} else {
		Quiz *lesson = [self.lessons objectAtIndex:(self.counter)];
		return lesson;
	}
}

- (void)countSection {
	NSFetchRequest *request =[[NSFetchRequest alloc] init];
	if (self.managedObjectContext_ == nil) {
		self.managedObjectContext_ = [(OntarioG1TestAppDelegate *)[[UIApplication sharedApplication] delegate]managedObjectContext];
	}
	NSEntityDescription *entity = [NSEntityDescription entityForName:@"Quiz"
											  inManagedObjectContext:managedObjectContext_];
	[request setEntity:entity];
	NSError *error;
	self.lessons = [[managedObjectContext_ executeFetchRequest:request error:&error] mutableCopy];
	[request release];
	for (int i = 0; i<[lessons count]; i++) {
		counter = i;
		NSLog(@"%@", self.currentLesson.topic);
	}
	for (int i = 0; i<[lessonSection count]; i++) {
		NSString *sectionName = [lessonSection objectAtIndex:i];
		NSLog(@"Section Name %@", sectionName);
		NSPredicate *predicate = [NSPredicate predicateWithFormat:@"topic==%@", sectionName];
		NSMutableArray *tempArray = [[self.lessons filteredArrayUsingPredicate:predicate] mutableCopy];
		NSLog(@"Array Count %i", [tempArray count]);
		//sectionCountNumber = [managedObjectContext_ countForFetchRequest:request error:&error];
//		NSLog(@"%i", sectionCountNumber);
		[sectionCount addObject:[NSNumber numberWithInteger:[tempArray count]]];

	}
	
}

For the first loop that goes through everything in the Array and gives the following
PHP: 
A
A
A
A
A
B
B
B
B
B
B
C
C
C
C
C
C
D
D
D
D
D
D
D
D

but when I apply the predicate to the array, I get the following:

PHP: 
Section Name A
Array Count 0
Section Name B
Array Count 0
Section Name C
Array Count 0
Section Name D
Array Count 1
Section Name E
Array Count 0

I don't understand why it's only picking up 1 for D and nothing else for the other letters.
 
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