A simple COCOA Asynchronous image loader class to use in your iPhone app.

This isnt a tutorial, this is just some source code that you might find useful. This class will load images in the background so it wont lock your UI up!

UPDATED:Please note that this post has a new updated version found here: UIImage From URL – Simplified (Using Blocks)

Here’s the header file :

@interface GGImageLoader : NSObject {
    NSURLConnection * connection;
    NSURL * url;
    NSMutableData * mutData;
    UIImage * image;
    id delegate;
}
 
@property ( nonatomic, retain ) UIImage * image;
 
- (id)initWithURL:(NSURL *)aURL;
- (void)setDelegate:(id)anObject;
- (void)load;
 
@end
 
@protocol GGImageLoaderProtocol
 
@required
- (void)imageLoader:(GGImageLoader *)loader
       didLoadImage:(UIImage *)anImage;
 
@optional
- (void)imageLoader:(GGImageLoader *)loader
    didReceiveError:(NSError *)anError;
 
@end

and heres the main file :

#import "GGImageLoader.h"
 
@implementation GGImageLoader
 
@synthesize image;
 
- (void)dealloc
{
    [super dealloc];
    [url release];
    [connection release];
    [mutData release];
    [image release];
}
 
- (id)initWithURL:(NSURL *)aURL
{
    url = [aURL retain];
    return self;
}
 
- (void)setDelegate:(id)anObject
{
    delegate = anObject;
}
 
- (void)load
{
    // SHOW NETWORK INDICATOR
 
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
 
    // SET UP THE REQUEST
 
    NSURLRequest * request = [[[NSURLRequest alloc] initWithURL:url] autorelease];
 
    // SET UP THE CONNECTION
 
    connection = [[NSURLConnection alloc] initWithRequest:request
                                                 delegate:self];
 
    // NEW MUT DATA
 
    mutData = [[[NSMutableData alloc] init] retain];
 
}
 
- (void)connection:(NSURLConnection *)connection
  didFailWithError:(NSError *)error
{
    if( [delegate respondsToSelector:@selector(imageLoader:didReceieveError:)] )
    {
        [delegate imageLoader:self
              didReceiveError:error];
    }
}
 
- (void)connection:(NSURLConnection *)connection
    didReceiveData:(NSData *)data
{
 
    // APPEND THE DATA
 
    [mutData appendData:data];
}
 
- (void)connectionDidFinishLoading:(NSURLConnection *)aConnection
{
 
    // ONCE LOADED HIDE NETWORK INDICATOR
 
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
 
    // RELEASE THE CONNECTION
 
    [connection release];
 
    // CREATE NEW UIIMAGE FROM THE DATA
 
    image = [[[UIImage alloc] initWithData:mutData] retain];
 
    if( [delegate respondsToSelector:@selector(imageLoader:didLoadImage:)] )
    {
        [delegate imageLoader:self
                 didLoadImage:image];
    }
 
}
 
@end

Its pretty self explanatory, meerly do the following to get it to work..

GGImageLoader * imageLoader = [[[GGImageLoader alloc] initWithURL:[NSURL URLWithString:@"myimageurlhere"]] retain];
[imageLoader setDelegate:self];
[imageLoader load];

The class also has delegate methods and a protocol to follow, so we know when the image has loaded, you can use the GGImageLoaderProtocol in your header file if you like.

- (void)imageLoader:(GGImageLoader *)imageLoader didReceieveError:(NSError *)anError{} - (void)imageLoader:(GGImageLoader *)imageLoader didLoadImage:(UIImage *)anImage{    // BE SURE TO RELEASE THE IMAGE LOADER  [imageLoader release];}

Thats about it, hope its helps some people out!

If ive made a mistake anywhere in this please say, it was a rush post!