GeekyGoodnessSoftware Developer

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@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

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#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 new] 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

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

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

6 comments

1. lilikindsli

   October 4, 2009 at 10:04 pm

   GJaldN I want to say – thank you for this!

   Log in to Reply
2. lockerrushing

   November 1, 2009 at 9:44 pm

   Thanks for the post. I am just starting out and was wondering if you could show me how to do a form post?

   I am trying to create a batch poster in cocoa. I will need to feed in an encoded cookie string and POST it to the server every 500 milliseconds.

   Any thoughts?

   Also, how does this work:
   - (void)connection:(NSURLConnection *)connection
   didReceiveData:(NSData *)data
   {

   I am coming from an AS background, what is this technique called?

   Thanks!

   Log in to Reply
3. Curtis Hard

   November 2, 2009 at 12:03 am

   Ill do a future post on posting to servers, whenever I get time.

   An NSURLConnection has delegate methods ( methods that are called when events happen, just like AS3′s EventDispatcher ), basically the NSURLConnection will stream the required NSURL contents via NSData through that function. Because they are received in parts we have to construct the overall data object, so as you can see, I have set up a NSMutableData object which im appending the NSData that is received. Its pretty simple.

   Also im a AS3 developer ;), its a bit like the ProgressEvent in AS3, apart from instead of a percent and bytes loaded / bytes total, it also gives you the data it recieves =].

   Hope that helps.

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4. lockerrushing

   November 2, 2009 at 7:15 am

   Thanks for the fast reply. Just ordered some cocoa books. I think I need to run through the basics first.

   Peace

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5. yves

   February 16, 2010 at 9:26 pm

   Hi, thank you for this – I had been looking for how do do that. I am still learning memory management, read a few books, etc… but I guess most examples I have seen were simple. If you are looking for an idea for your next log, explaining the retain and release in GGImageLoader would be great. Thank you.

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6. Curtis Hard

   February 16, 2010 at 9:35 pm

   Hello yves,

   Its really simple, basically, think of it like this : anything you allocate will be automatically released, so [[UIView alloc] init]; will be picked up my the run loops etc and released accordingly. When you stick retain on it, it puts the retain count up by one, starts with 0, then you +1 to it, so now when the auto release pools run, it will ignore your object and wont get released. Likewise, if you run release on it, it will get rid of it from memory. If you dont retain objects when you need to, then problems occur when your trying to call the object, but it has already been released from memory, thus causing epic fail.

   If that helps what so ever…and remember to follow @caffeinatedapp for my latest news on my app ;)

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