多线程之NSOperation

#import "ViewController.h"
#define kURL @"http://avatar.csdn.net/2/C/D/1_totogo2010.jpg"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc]initWithTarget:self
                                                                           selector:@selector(downloadImage:)
                                                                             object:kURL];

    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    [queue addOperation:operation];
	// Do any additional setup after loading the view, typically from a nib.
}

-(void)downloadImage:(NSString *)url{
    NSLog(@"url:%@", url);
    NSURL *nsUrl = [NSURL URLWithString:url];
    NSData *data = [[NSData alloc]initWithContentsOfURL:nsUrl];
    UIImage * image = [[UIImage alloc]initWithData:data];
    [self performSelectorOnMainThread:@selector(updateUI:) withObject:image waitUntilDone:YES];
}
-(void)updateUI:(UIImage*) image{
    self.imageView.image = image;
}