How to Cancel all NSURLConnections in Background in iOS

Question

I am downloading some Images (approx 200-300 thumb images) on Using NSURLCOnnections. I have array of urls of these images. The connection starts to download these images. But in certain case i want to cancel all these downloading. How it is possible. Can i cancel all these NSURLConnections.

Answer 1

Will be better to create NSOperationQueue and work with NSURLConnection through this queue.

For example:

NSOperationQueue *queue = [NSOperationQueue new];
NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(sendRequest)];


- (void) sendRequest {
    NSURL *url = [NSURL URLWithString:@"http://www.google.com"];
    NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:url];
    NSURLConnection *theConnection = [[[NSURLConnection alloc] initWithRequest:theRequest delegate:self] autorelease];
    ...
}

NSOperationQueue has method cancelAllOperations

Answer 2

[connection cancel]用于取消NSURLConnection。

Answer 3

I would use a synchronous NSURLConnection in combination with an NSOperationQueue to download the data:

[queue addOperationWithBlock:^{
    NSData *data = [NSURLConnection
        sendSynchronousRequest:…
        returningResponse:… error:…];
}];

This way you can easily control the number of concurrent downloads and cancel the unfinished ones using [queue cancelAllOperations] . Note that cancelling the queue won't stop the downloads that have already started, but that won't be a problem if you're downloading just small thumbnails and have a decent concurrent download limit.

Synchronous NSURLConnection mode has the advantage of being much easier to use than the asynchronous delegation API.