Question

I am downloading a bitmap using NSURLConnection. I set the delegate to self, and implement the methods connection:didReceiveData and connectionDidFinishLoading. When data is received, I store it in an NSMutableData object (called input), and then at the end of the connection, I use this to create the bitmap. The problem is that I receive the data in connection:didReceiveData but it is null in connection:DidFinishLoading. How do I fix this?

- (void)start
{
    NSURL *url = [NSURL URLWithString:src];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

    connection = [[NSURLConnection alloc] initWithRequest:request
                                                 delegate:self
                                         startImmediately:YES];
}

- (void)connection:(NSURLConnection *)conn
    didReceiveData:(NSData *)d
{
    NSLog(@"Data Received: %@", d);//This prints the correct data
    //Add data chunk to input
    [input appendData:d];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)conn
{
    CPLog(@"Finished Receiving bitmap from server. Data received with length %d: %@", [input length], input);//this prints length 0 and a value of (null)
    CFDataRef imgData = (__bridge CFDataRef) input;
    CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData (imgData);
    CGImageRef image;
    if (!imgDataProvider)
    {
        NSLog(@"Request Failed!");//happens every time
        [callback handleBitmap:nil];
        return;
    }

    image = CGImageCreateWithJPEGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault);


    [callback handleBitmap:image];
    return;

}

Answer 1

You should allocate memory for input property. Usually it is done before starting new url connection:

- (void)start
{
    self.input = [NSMutableData data];
    // .... init and start url connection
}