Question

The following are methods that I am using to retrieve data from a server while displaying a UIActivityIndicator. I’m trying to put these methods in the app delegate and then call them from other classes, but I don’t know how to return my JSONData. Can anybody help with this?

 -(void)startProcess:(NSString *)buildURL{


UIActivityIndicatorView *aInd = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActionSheetStyleBlackTranslucent];

[aInd setFrame:CGRectMake(0, 0, 50, 50)];
[aInd startAnimating];

// then call the timeCOnsumingmethod in separate thread.
[NSThread detachNewThreadSelector:@selector(getData:) toTarget:self withObject:buildURL];
} 

- (void)getData:(NSString *)buildURL{


NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

// Query our database for a restaurant's menus
NSURL *url = [NSURL URLWithString:buildURL];
NSError *e;
NSString *jsonreturn = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&e];

NSData *jsonData = [jsonreturn dataUsingEncoding:NSUTF32BigEndianStringEncoding];
// NSError *error = nil;

[self performSelectorOnMainThread:@selector(endProcess:) withObject:jsonData waitUntilDone:YES];
[pool release];

//return jsonData;
}

- (IBAction)endProcess:(NSData *)jsonData{
// ??????????
return jsonData;
}

Answer 1

Not sure why got downvoted but your approach is all wrong. Here’s what you want to do:

• Add the UIActivityIndicatorView
• Use NSURLConnection to asynchronously retrieve the data
• Use NSJSONSerialization to decode the received JSON into a NSDictionary or NSArray
• Remove the UIActivityIndicatorView

Your best bet would be to implement this as a separate class that takes a delegate object. You could implement a delegate protocol to indicate states like ‘started network activity’ (which your delegate could use to add a spinner view), and ‘received data’ (which would pass the decoded object back to the delegate – the delegate could then remove the spinner).

One of the benefits of this approach is you can easily set it up so that the connection/request is canceled when the object deallocs. Then you just store the request object as a property on your delegate, and when your delegate goes away, it deallocs the request, which cancels/cleans up properly.