How to use dispatch_async_f?

问题

The function that I want queued takes no parameters. What do I pass in as paramContext? Passing in NULL generates the compile error "Invalid use of void expression". I do not want to add a parameter to my function just to make it compile - how do I make this work?

Mac OS X Snowleopard, Xcode 3.2.6 with Objective-C

回答1:

You need to wrap the function somehow. The easiest way is actually to use dispatch_async() instead, as in

dispatch_async(queue, ^{ myFunc() });

回答2:

While you can just pass 0/NULL for the context argument, dispatch_async_f() takes void (*)(void*) as the function parameter, you can't pass it a function that takes no arguments.

You need to either change your function to take a void* parameter:

void func(void*) {}

... or, if you can't, wrap it:

void orig(void) {}
void wrapper(void*) { orig(); }

// ...
dispatch_async_f(queue, 0, &wrapper);

来源：https://stackoverflow.com/questions/9320142/how-to-use-dispatch-async-f