Cache URL images iphone UITableview

ImageCache.h

#import <Foundation/Foundation.h>

@interface ImageCache : NSObject

@property (nonatomic, retain) NSCache *imgCache;

#pragma mark - Methods

+ (ImageCache*)sharedImageCache;

- (void) AddImage:(NSString *)imageURL img:(UIImage *)image;

- (UIImage*) GetImage:(NSString *)imageURL;
- (BOOL) DoesExist:(NSString *)imageURL;


@end

ImageCache.m

#import "ImageCache.h"

@implementation ImageCache

@synthesize imgCache;

#pragma mark - Methods

static ImageCache* sharedImageCache = nil;

+(ImageCache*)sharedImageCache
{
    @synchronized([ImageCache class])
    {
        if (!sharedImageCache)
            sharedImageCache= [[self alloc] init];

        return sharedImageCache;
    }

    return nil;
}

+(id)alloc
{
    @synchronized([ImageCache class])
    {
        NSAssert(sharedImageCache == nil, @"Attempted to allocate a second instance of a singleton.");
        sharedImageCache = [super alloc];

        return sharedImageCache;
    }

    return nil;
}

-(id)init 
{
    self = [super init];
    if (self != nil) 
    {
        imgCache = [[NSCache alloc] init];
    }

    return self;
}

- (void) AddImage:(NSString *)imageURL img:(UIImage *)image

{
    [imgCache setObject:image forKey:imageURL];
}

- (NSString*) GetImage:(NSString *)imageURL
{
    return [imgCache objectForKey:imageURL];
}

- (BOOL) DoesExist:(NSString *)imageURL
{
    if ([imgCache objectForKey:imageURL] == nil)
    {
        return false;
    }

    return true;
}


@end

Example

UIImage *image;

    // 1. Check the image cache to see if the image already exists. If so, then use it. If not, then download it.

    if ([[ImageCache sharedImageCache] DoesExist:imgUrl] == true)
    {
        image = [[ImageCache sharedImageCache] GetImage:imgUrl];
    }
    else
    {

        NSData *imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: imgUrl]];
        image = [[UIImage alloc] initWithData:imageData];

        // Add the image to the cache 
        [[ImageCache sharedImageCache] AddImage:imgUrl img:image];

(OR)

[NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:[NSURL URLWithString: imgUrl]] queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

                UIImage *image = [UIImage imageWithData:data];

                [[ImageCache sharedImageCache] AddImage:imgUrl img:image];

            }];

    }