KVO of NSOperationQueue

KVOOperationQueue.m

@interface KVOOperationQueue()
@property(nonatomic, strong) NSOperationQueue *queue;
@end

@implementation KVOOperationQueue

-(id)init{
    self = [super init];
    if(self){
        filePath = filename;
        blockOperation = [[NSOperation alloc]init];
        //initialize the queue
        _queue = [[NSOperationQueue alloc]init];
        //!!! adding observer of the operationCount property to self
    
        [self.queue addObserver:self forKeyPath:@"operationCount" options:NSKeyValueObservingOptionNew context:nil];
        
    }
    return self;
}
/*
 This method observes changes to to all objects and keypaths, in our case we are looking for operationCount property 
The change dictionary stores old and new values of the observed property. If the new value is equal to 0 it means that queue 
 doesn't have any more completed operations.
 
*/
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if([keypath isEqualToString:@"operationCount"]){
       if([[change objectForKey:@"new"] isEqual:@0]){
            NSLog(@"Completed");
        }
    }
    
}

//This method adds operations to the operation queue
-(void)someOperationsWithQueues{
  for(int i =1; i<1000;i++){
        [_queue addOperationWithBlock:^{
            //background operation
        }];
    }
}

@end