NSTimer does not support block until the release of ios 10. This gist can serve in that situation.

NSTimerBlock.h

#import <Foundation/Foundation.h>


//
//  HISTORY...
//
//  from ios 10 simillar functionality is given which is initialized
//  with a block, but we need to support the older version too,
//  thats why this class is been introduced
//
typedef void (^NSTimerExecutionBlock)(NSTimer*);

@interface NSTimerBlock : NSObject

-(instancetype)initWithInterval:(NSTimeInterval)interval withExecutionBlock:(NSTimerExecutionBlock)block repeats:(BOOL)repeat;

-(void)stopTimer;

@end

NSTimerBlock.m

#import "NSTimerBlock.h"

@implementation NSTimerBlock
{
    NSTimer *timer;
    NSTimerExecutionBlock execBlock;
}

-(instancetype)initWithInterval:(NSTimeInterval)interval withExecutionBlock:(NSTimerExecutionBlock)block repeats:(BOOL)repeat
{
    self = [super init];
    
    if(self)
    {
        //
        //  saving the code block,
        //  which is to be executed later
        //
        execBlock = block;
        
        //
        //  initiate the timer
        //
        timer = [NSTimer scheduledTimerWithTimeInterval:interval
                                                 target:self
                                               selector:@selector(timerFired:)
                                               userInfo:nil
                                                repeats:repeat];
    }
    return self;
}

-(void)stopTimer
{
    [timer invalidate];
    timer = nil;
}

#pragma mark timer selector
-(void)timerFired:(NSTimer*)tmr
{
    if(execBlock)
    {
        //
        //  some sort of execution block is
        //  present for processing
        //  so we will execute
        //
        execBlock(tmr);
    }
    else
    {
        [tmr invalidate];
        tmr = nil;
    }
}

@end

Do you need NSTimer with Block feature ?, ios 10 NSTimer has it. But what for the previous version ? This can serve as well the same purpose with more cleaner code.

How to use::

[[NSTimerBlock alloc] initWithInterval:2.0
                              withExecutionBlock:^(NSTimer *) {
                                 //code that you want to execute after 2.0 seconds
                            }
                                                repeats:NO];

if you want to suppress unused warning put them inside like following

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-value"
        [[NSTimerBlock alloc] initWithInterval:2.0

                            withExecutionBlock:^(NSTimer *) {

                                [[UIApplication sharedApplication] endIgnoringInteractionEvents];

                                [self dismissViewControllerAnimated:YES completion:^{
                                    [calleeView removeCalleeWithKeyNumber:nmbr];
                                }];
                            }
                                       repeats:NO];
#pragma clang diagnostic pop