gistfile1.m

@protocol DDAsyncTaskDelegate <NSObject>
- (void)setResult:(id)result;
- (void)setError:(NSError *)error;
@end

@protocol DDAsyncTask <NSObject>
- (void)startWithDelegate:(id<DDAsyncTaskDelegate>)delegate;
@end

id<DDFuture> DDStartAsyncTask(id<DDAsyncTask> asyncTask);


@interface UrlConnectionTask : NSObject <DDAsyncTask>
{
    id<DDAsyncTaskDelegate> _delegate;
    NSURLConnection * _connection;
    NSMutableData * _responseData;
}

+ (id)urlConnectionTaskWithUrlRequest:(NSURLRequest *)request;

- (id)initWithUrlRequest:(NSURLRequest *)request;

- (void)startWithDelegate:(id<DDAsyncTaskDelegate>)delegate;

@end


@implementation UrlConnectionTask

+ (id)urlConnectionTaskWithUrlRequest:(NSURLRequest *)request;
{
    id o = [[self alloc] initWithUrlRequest:request];
    return [o autorelease];
}

- (id)initWithUrlRequest:(NSURLRequest *)request;
{
    self = [super init];
    if (self == nil)
        return nil;
    
    _connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
    
    return self;
}

- (void)dealloc
{
    [_connection release];
    [_responseData release];
    [super dealloc];
}

- (void)startWithDelegate:(id<DDAsyncTaskDelegate>)delegate;
{
    _delegate = [delegate retain];
    [_connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
    [_connection start];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [_delegate setError:error];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [_delegate setResult:_responseData];
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [_responseData release];
    _responseData = [[NSMutableData alloc] init];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [_responseData appendData:data];
}

@end

{
    NSURL * url = [NSURL URLWithString:@"http://www.example.com/"];
    NSURLRequest * request = [NSURLRequest requestWithURL:url];
    UrlConnectionTask * urlConnectionTask = [[UrlConnectionTask alloc] initWithUrlRequest:request];
    id<DDFuture> futureData = DDStartAsyncTask(urlConnectionTask);

    // This runs the run loop waiting for the result
    NSError * error = nil;
    NSData * response = [futureData result:&error];

    if (response != nil) {
        NSString * responseString = [[[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding] autorelease];
        NSLog(@"String:\n%@", responseString);
    } else {
        NSLog(@"Error: %@ %@", error, [error userInfo]);
    }
}