Block variables in Objective-C - objective-c

Question

I have a questions about blocks in Objective-C.
For example I have this code:
__block int count = 0;
void (^someFunction)(void) = ^(void){
count = 4;
};
count +=2;
What would be the proper way to write the same piece of code so the count will become 6, not 2 ?!
Thank you!
I should probably show the actual code because my previous question was blurry.
EDIT:
__block CMTime lastTime = CMTimeMake(-1, 1);
__block int count = 0;
[_imageGenerator generateCGImagesAsynchronouslyForTimes:stops
completionHandler:^(CMTime requestedTime, CGImageRef image, CMTime actualTime,
AVAssetImageGeneratorResult result, NSError *error)
{
if (result == AVAssetImageGeneratorSucceeded)
{
NSImage *myImage = [[NSImage alloc] initWithCGImage:image size:(NSSize){50.0,50.0}];
[arrOfImages addObject:myImage];
}
if (result == AVAssetImageGeneratorFailed)
{
NSLog(#"Failed with error: %#", [error localizedDescription]);
}
if (result == AVAssetImageGeneratorCancelled)
{
NSLog(#"Canceled");
}
if (arrOfImages.count > 5)
{
NSLog(#"here");
}
count++;
}];
int f = count+1;
after 10 iterations count is 0...why?!?!

Answer 1

You are not executing the block (calling a block someFunctionmight be a misleading thing)
__block int count = 0;
void (^someBlock)(void) = ^{
count = 4;
};
someBlock();
count +=2;

Answer 2

Call block like this:
someFunction();
So that would be:
__block int count = 0;
void (^someFunction)(void) = ^(void){
count = 4;
};
// call block
someFunction();
count +=2;

Answer 3

Look at the name of the method you are calling; generateCGImagesAsynchronouslyForTimes: completionHandler:.
Asynchronously means that it executes in a different thread (likely via a queue and, as #newaccount points, it may likely be re-scheduled for future execution on the current queue/thread) and the method returns immediately. Thus, when you set f=count+1;, the completion block hasn't even been executed yet because none of the image loads in background threads have been completed.
You need to make a call from that completion block back to your code that needs to respond to the completion. i.e.
^() {
....
dispatch_async(dispatch_get_main_queue(), ^{[self heyManAnImageLoadedDude];});
....
}