How to pass a SEL to dispatch_async method - objective-c

Question

I am trying to create a generic method that takes a SEL as a parameter and passes it to dispatch_async for execution, but i am clueless how to execute the passed in SEL.
Can anyone here help me please.
// Test.m
-(void) executeMe
{
NSLog(#"Hello");
}
- (void)viewDidLoad
{
[super viewDidLoad];
SEL executeSel = #selector(executeMe);
[_pInst Common_Dispatch: executeSel];
}
// Common.m
-(void) Common_Dispatch:(SEL) aSelector
{
dispatch_async(iDispatchWorkerQueue, ^(void) {
// How to execute aSelector here?
});
}

Answer 1

You need to also have a "target" parameter on your Common_Dispatch method since you need to call the selector on a specific object.
- (void)viewDidLoad {
[super viewDidLoad];
SEL executeSel = #selector(executeMe);
[_pInst Common_Dispatch:executeSel target:self];
}
- (void)Common_Dispatch:(SEL)aSelector target:(id)target {
dispatch_async(iDispatchWorkerQueue, ^(void) {
[target performSelector:aSelector];
});
}
BTW - standard naming conventions state that method names should begin with lowercase and use camelCase. Your method should be commonDispatch.

Answer 2

Alternatively, you could use a block parameter, e.g.
- (void)commonDispatch:(void (^)(void))block
{
dispatch_async(iDispatchWorkerQueue, block);
}
You'd then invoke that as:
[_pInst commonDispatch:^{
[self executeMe];
}];
This way, you could use this dispatcher to call methods like executeMe which take no parameters, or to dispatch methods that take lots of parameters, e.g.:
[_pInst commonDispatch:^{
[self executeOtherMethodForURL:url requestType:type priority:priority];
}];
Or more complicated situations, too:
[_pInst commonDispatch:^{
[self executeOtherMethodForURL:url requestType:type priority:priority];
dispatch_async(dispatch_get_main_queue(), ^{
// update my UI to say that the request is done
});
}];

Answer 3

You simply call the performSelector method, like this:
[self performSelector:aSelector];
There are other useful overrides to performSelector you'll find.
Edit
The target of the selector will also have to be passed as a param:
// Test.m
-(void) executeMe
{
NSLog(#"Hello");
}
- (void)viewDidLoad
{
[super viewDidLoad];
SEL executeSel = #selector(executeMe);
[_pInst Common_Dispatch: executeSel target:self];
}
// Common.m
-(void) Common_Dispatch:(SEL) aSelector target:(id)target
{
dispatch_async(iDispatchWorkerQueue, ^(void) {
[target performSelector:aSelector];
});
}