SPCategoriesViewController.m

#import "SPCategoriesViewController.h"

@interface SPCategoriesViewController () {
    NSArray *recipeImages;
    NSString *parentID;
}

@end

@implementation SPCategoriesViewController

@synthesize segmentedControl;

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"mainlogo.png"] forBarMetrics:UIBarMetricsDefault];
    [self setNeedsStatusBarAppearanceUpdate];
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent animated:NO];

    [self.collectionView registerClass:[UICollectionViewCell class]forCellWithReuseIdentifier:@"Cell"];
    self.collectionView.delegate = self;
    self.collectionView.dataSource=self;

    NSData *allCategoriesData = [[NSData alloc] initWithContentsOfURL:
                                 [NSURL URLWithString:@"http://example.com/getData"]];
    NSError *error;
    self.allCategories = [NSJSONSerialization
                          JSONObjectWithData:allCategoriesData
                          options:kNilOptions
                          error:&error];
    [self.collectionView reloadData];
}


//set collection view margin
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
    return UIEdgeInsetsMake(8, 8, 8, 8);
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return [self.allCategories count];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    UIImageView *recipeImageView = (UIImageView *)[cell viewWithTag:100];
    NSDictionary *category = [self.allCategories objectAtIndex:[indexPath row]];

    UILabel *titleLabel = (UILabel *)[cell viewWithTag:200];
    [titleLabel setText:[category objectForKey:@"name"]];

    dispatch_async(dispatch_get_global_queue(0,0), ^{
        NSData * data = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString:[category objectForKey:@"image"]]];
        if ( data == nil )
            return;
        dispatch_async(dispatch_get_main_queue(), ^{
            recipeImageView.image = [UIImage imageWithData: data];
        });
    });

    cell.layer.cornerRadius = 3.0;
    cell.layer.masksToBounds = NO;
    cell.layer.shadowColor = [UIColor blackColor].CGColor;
    cell.layer.shadowOffset = CGSizeMake(2, 2);
    cell.layer.shadowOpacity = 0.5;
    cell.layer.shadowRadius = 1.2;
    cell.clipsToBounds = NO;

    return cell;
}

- (IBAction)segmentedControlAction:(id)sender {

    switch (segmentedControl.selectedSegmentIndex) {
        case 0:
            parentID = @"1";
            break;
        case 1:
            parentID = @"12";
            break;
        case 2:
            parentID = @"18";
            break;
    }
    NSLog(@"%@", parentID);

}
@end