UIIMagePickerController & NSURLConnection - objective-c

Question

UIImagePickerController freezes while I think the Image is being compressed or being sent by NSURLConnection although I'm not convinced it's the later.
What I want is, all this to be done in the background. Instead when I pick a photo from the library, the Screen freezes for what feels like forever. This isn't optimal, obviously. What approach should I take here?
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo
{
int i = 0;
NSString *uniquePath = [NSHomeDirectory() stringByAppendingPathComponent:#"Documents/selectedImage.png"];
while ([[NSFileManager defaultManager] fileExistsAtPath:uniquePath])
{
uniquePath = [NSString stringWithFormat:#"%#/%#-%d.%#", [NSHomeDirectory() stringByAppendingPathComponent:#"Documents"], #"selectedImage", ++i, #"png"];
}
NSLog(#"Writing selected Image to Documents Folder, %#", uniquePath);
dataForPNGFile = UIImagePNGRepresentation(img);
if (!dataForPNGFile) return NO;
[UIImagePNGRepresentation(img) writeToFile:uniquePath atomically:YES];
UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil);
[[self parentViewController] dismissModalViewControllerAnimated:YES];
[picker release];
NSString *urlString = #"http://localhost:3000/photos";
NSURL *url = [NSURL URLWithString:urlString];
NSString *boundary = #"----1010101010";
NSString *contentType = [NSString stringWithFormat:#"multipart/form-data; boundary=%#",boundary];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:#"POST"];
[request addValue:contentType forHTTPHeaderField: #"Content-Type"];
NSString *photoPath = [[NSBundle mainBundle] pathForResource:#" my-photo " ofType:#"jpg"];
NSData *photoData = [NSData dataWithContentsOfFile:photoPath];
NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[#"Content-Disposition: form-data; name=\"photo-description\"\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[#"testing 123" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"\r\n--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
// [body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"photo-file\"; filename=\"%#\"\r\n", " my-photo.jpg"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[#"Content-Type: image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:photoData];
[body appendData:[[NSString stringWithFormat:#"\r\n--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[#"Content-Disposition: form-data; name=\"tags\"\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[#"random,test,example" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"\r\n--%#--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[request setHTTPBody:body];
[request addValue:[NSString stringWithFormat:#"%d", body.length] forHTTPHeaderField: #"Content-Length"];
[[NSURLConnection alloc] initWithRequest:request delegate:self];
}

Answer 1

You should use:
detachNewThreadSelector:toTarget:withObject:
Detaches a new thread and uses the specified selector as the thread entry point.
+ (void)detachNewThreadSelector:(SEL)aSelector toTarget:(id)aTarget withObject:(id)anArgument
Documentation here: NSThread
This will create a new thread for the operation that is eating up the cpu, so your UI isn't affected remember to create a NSAutoreleasePool for the new thread, as only the main thread gets a NSAutoreleasePool pool by default.
So at the beginning of your selector do:
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
//and at the end:
[pool drain]: