Question

I’d like to create a macro for GCD calls like for example:

dispatch_async(dispatch_get_main_queue(), ^{
    stuff....
});

the macro could look something like this:
main(^{…})?

Not sure how to write it. Any suggestion?

thank you

Answer 1

You can define macros like this:

#define ASYNC(...) dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ __VA_ARGS__ })
#define ASYNC_MAIN(...) dispatch_async(dispatch_get_main_queue(), ^{ __VA_ARGS__ })

First one will invoke the code asynchronously on unspecified thread (do all long running tasks using it) and the second one will invoke the block asynchronously on the main thread (do all UI related stuff using it).

You can combine both. Let’s say you want to grab something from the network and update UI, you can write:

ASYNC({
  NSString *result = [[NSString alloc] initWithContentsOfURL: ...];
  ASYNC_MAIN({
    self.myTextField.string = result;
    [result release];
  });
});

You add curly braces to make Xcode indent the code properly.

Please note where retain/release calls are made. This is powerful technique which will make your code readable.