ViewController.m from CoreData tutorial http://www.youtube.com/watch?v=mEAav7dM4hk

ViewController.m

//
//  ViewController.m
//  coreDataTutorial
//
//  Created by Naoya Makino on 12-10-25.
//  Copyright (c) 2012 Naoya Makino. All rights reserved.
//

#import "ViewController.h"
#import "AppDelegate.h"

@interface ViewController ()
{
    NSManagedObjectContext *context;
}

@end

@implementation ViewController
@synthesize firstnameTextField;
@synthesize lastnameTextField;
@synthesize displayLabel;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    
    [[self firstnameTextField]setDelegate:self];
    [[self lastnameTextField]setDelegate:self];
}

- (void)viewDidUnload
{
    [self setFirstnameTextField:nil];
    [self setLastnameTextField:nil];
    
    AppDelegate *appdelegate = [[UIApplication sharedApplication]delegate];
    context = [appdelegate managedObjectContext];
    [self setDisplayLabel:nil];
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

- (IBAction)addPersonButton:(id)sender {
    NSEntityDescription *entitydesc = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:context];
    NSManagedObject *newPerson = [[NSManagedObject alloc]initWithEntity:entitydesc insertIntoManagedObjectContext:context];
    
    [newPerson setValue:self.firstnameTextField.text forKey:@"firstname"];
    [newPerson setValue:self.lastnameTextField.text forKey:@"lastname"];
    
    NSError *error;
    [context save:&error];
    
    self.displayLabel.text = @"Person added.";
}

- (IBAction)searchPersonButton:(id)sender {
    NSEntityDescription *entitydesc = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:context];
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    [request setEntity:entitydesc];
    
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"firstname Like %@ and lastname like %@", self.firstnameTextField.text, self.lastnameTextField.text];
    [request setPredicate:predicate];
    
    NSError *error;
    NSArray *matchingData = [context executeFetchRequest:request error:&error];
    
    if (matchingData.count <= 0)
    {
       self.displayLabel.text = @"No person found.";
    }
    else {
        NSString *firstName;
        NSString *lastName;
        
        for (NSManagedObject *obj in matchingData) {
            firstName = [obj valueForKey:@"firstname"];
            lastName = [obj valueForKey:@"lastname"];
        }
        self.displayLabel.text = [NSString stringWithFormat:@"Firstname: %@, Lastname: %@", firstName, lastName];
    }
}

- (IBAction)deletePersonButton:(id)sender {
    NSEntityDescription *entityDec = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:context];
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    [request setEntity:entityDec];
    
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"firstname Like %@", self.firstnameTextField.text];
    [request setPredicate:predicate];
    NSError *error;
    NSArray *matchingData = [context executeFetchRequest:request error:&error];
    
    if(matchingData.count <= 0)
    {
        self.displayLabel.text = @"no person deleted.";
    }
    else
    {
        int count = 0;
        for (NSManagedObject *obj in matchingData) {
            [context deleteObject:obj];
            ++count;
        }
        [context save:&error];
        self.displayLabel.text = [NSString stringWithFormat:@"%d persons deleted", count];
    }
}

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    return [textField resignFirstResponder];
}
@end