Add continuation block to method - objective-c

Question

I have a singleton that displays status messages:
+ (FFStatusDisplay*) sharedInstance
{
static FFStatusDisplay* sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken,
^{
sharedInstance = [[FFStatusDisplay alloc] init];
});
return sharedInstance;
}
- (void) showStatus:(NSString*)message Timeout:(float)timeout Controller:(UIViewController*)controller
{
if (![self isDisplaying])
{
[self setIsDisplaying:YES];
[self setStatusAlert:[UIAlertController alertControllerWithTitle:nil message:message preferredStyle:UIAlertControllerStyleAlert]];
[controller presentViewController:[self statusAlert] animated:YES completion:
^{
[NSTimer scheduledTimerWithTimeInterval:timeout target:self selector:#selector(timerExpired:) userInfo:nil repeats:NO];
}];
}
}
- (void)timerExpired:(NSTimer *)timer
{
[[self statusAlert] dismissViewControllerAnimated:YES completion:nil];
[self setStatusAlert:nil];
[self setIsDisplaying:NO];
}
I would like to modify showStatus so that I can optionally call it with a completion block that executes after the message is removed by the timer. I think the declaration should be something like this:
- (void) showStatus:(NSString*)message Timeout:(float)timeout Controller:(UIViewController*)controller withBlock:(nullable id (^)(void))block;
But I don't know how to call the block in the body of the implementation. What I've been trying isn't right:
{
if (![self isDisplaying])
{
[self setIsDisplaying:YES];
[self setStatusAlert:[UIAlertController alertControllerWithTitle:nil message:message preferredStyle:UIAlertControllerStyleAlert]];
[controller presentViewController:[self statusAlert] animated:YES completion:
^{
[NSTimer scheduledTimerWithTimeInterval:timeout target:self selector:#selector(timerExpired:) userInfo:nil repeats:NO];
}];
}
block; //this isn't right
}
Can someone show me how to do this?
Thanks

Answer 1

In Objective-C, you call a block like a C function:
block();
That being said, if you want it to fire after your timer has fired, you'll need to add some mechanism to hang onto the block and call it from your timerExpired: method