how to use sendAsynchronousRequest:queue:completionHandler:

Question

Two part question

Part one: I am trying to create an ASynchronous request to my database. I am currently doing it Synchronously however I want to learn both ways to better my understanding of whats going on.

Currently I have set up my Synchronous call like this.

- (IBAction)setRequestString:(NSString *)string
{
    //Set database address
    NSMutableString *databaseURL = [[NSMutableString alloc] initWithString:@"http://127.0.0.1:8778/instacodeData/"]; // imac development

    //PHP file name is being set from the parent view
    [databaseURL appendString:string];

    //call ASIHTTP delegates (Used to connect to database)
    NSURL *url = [NSURL URLWithString:databaseURL];

    //SynchronousRequest to grab the data
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSError *error;
    NSURLResponse *response;

    NSData *result = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
    if (!result) {
        //Display error message here
        NSLog(@"Error");
    } else {

        //TODO: set up stuff that needs to work on the data here.
        NSString* newStr = [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];
        NSLog(@"%@", newStr);
    }
}

I think what I need to do is replace the call

NSData *result = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

with the ASynchronous version

sendAsynchronousRequest:queue:completionHandler:

however I'm not sure what to pass to queue or completionHandler... Any examples/solutions would be greatly appreciated.

Part two: I have been reading about multi tasking and I would like to support it by making sure my connection requests complete if there is an interrupt. I have been following this example

In it it explains how to gain more time if an interrupt occurs, I understand what its doing.. but not how to apply it to this connection? if you have any examples/tutorials to help me figure out how to apply it that would be awesome!

Answer 1

PArt 1:

NSURL *url = [NSURL URLWithString:urlString];

NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];

[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
    if ([data length] > 0 && error == nil)
        [delegate receivedData:data];
    else if ([data length] == 0 && error == nil)
        [delegate emptyReply];
    else if (error != nil && error.code == ERROR_CODE_TIMEOUT)
        [delegate timedOut];
    else if (error != nil)
        [delegate downloadError:error];
}];