Run method on main thread from another thread - cocoa

Question

My model class has to get some data from the internet. So I decided to run it on another thread so the ui doesn't freeze.
So when an object wants some data it first asks the model using a method of this type:
- (void)giveMeSomeData:(id)object withLabel:(id)label {
objectAsking= object;
theLabel= label;
NSThread* thread= [[NSThread alloc] initWithTarget:self selector:#selector(getTheDataFromInternet) object:nil];
[thread start];
}
- (void)getTheDataFromInternet {
//getting data...
theData= [dataFromInternet retain]; //this is the data the object asked for
[self returnObjectToAsker];
}
- (void)returnObjectToAsker {
[objectAsking receiveData:theData withLabel:theLabel];
}
As I'm still a newbie, can you tell me if it's a good pattern?
Thanks!

Answer 1

Your setup is pretty much correct. You never want to initiate any sort of network connection on the main thread.
As it currently stands, -returnObjectToAsker will be executed on the background thread.
You'd probably be interested in -[NSObject performSelectorOnMainThread:withObject:waitUntilDone:].
Or if you wanted to something with Grand Central Dispatch (iOS 4+, Mac OS X 10.6+), you could do:
#import <dispatch/dispatch.h>
- (void)giveMeSomeData:(id)object withLabel:(id)label {
dispatch_async(dispatch_get_global_queue(0,0), ^{
//this runs on a background thread
//get data from the internet
dataFromTheInternet = ...;
dispatch_async(dispatch_get_main_queue(), ^{
[object receiveData:dataFromTheInternet withLabel:label];
//this runs on the main thread. Use theData
});
});
}
Since the blocks capture their environment, you wouldn't even have to save off object and label into ivars. :)