Multithreading Application in iphone programming?

Here I am explain you how to create threading in iphone. Here we will create two separate threads where one will increase counter and another will decrease counter. I am giving you complete code snippets as well as source code also.

devangViewController .h

#import <UIKit/UIKit.h>
@interface devangViewController : UIViewController
{    NSOperationQueue *operationQueue;
}
@property (weak, nonatomic) IBOutlet UILabel *counter1_lbl;
@property (weak, nonatomic) IBOutlet UILabel *counter2_lbl;
-(void)counter1;
-(void)counter2;
@end

devangViewController .m implementation file

#import "devangViewController.h"
@interface devangViewController ()
@end
@implementation devangViewController
@synthesize counter1_lbl,counter2_lbl;
- (void)viewDidLoad
{
    [super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
 
    operationQueue = [NSOperationQueue new];
 
    // Create a new NSOperation object using the NSInvocationOperation subclass.
    // Tell it to run the counterTask method.
    NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self
                                                                            selector:@selector(counter1)
                                                                              object:nil];
    // Add the operation to the queue and let it to be executed.
    [operationQueue addOperation:operation];
 
    operation = [[NSInvocationOperation alloc] initWithTarget:self
                                                     selector:@selector(counter2)
                                                       object:nil];
    [operationQueue addOperation:operation];

}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
-(void)counter1{
    // Make a BIG loop and every 100 repeats let it update the label1 UILabel with the counter's value.
    for (int i=0; i<100000; i++) {
     
            // Notice that we use the performSelectorOnMainThread method here instead of setting the label's value directly.
            // We do that to let the main thread to take care of showing the text on the label
            // and to avoid display problems due to the loop speed.
            [counter1_lbl performSelectorOnMainThread:@selector(setText:)
                                     withObject:[NSString stringWithFormat:@"%d", i]
                                  waitUntilDone:YES];
     
    }
 
    // When the loop gets finished then just display a message.
    [counter1_lbl performSelectorOnMainThread:@selector(setText:) withObject:@"Thread #1 Complete " waitUntilDone:NO];
}

-(void)counter2{
    // We need a custom color to work with.
    for (int i=100000; i>0; i--) {
                    // Notice that we use the performSelectorOnMainThread method here instead of setting the label's value directly.
            // We do that to let the main thread to take care of showing the text on the label
            // and to avoid display problems due to the loop speed.
            [counter2_lbl performSelectorOnMainThread:@selector(setText:)
                                           withObject:[NSString stringWithFormat:@"%d", i]
                                        waitUntilDone:YES];
    }
 
    // When the loop gets finished then just display a message.
    [counter2_lbl performSelectorOnMainThread:@selector(setText:) withObject:@"Thread #2 Complete " waitUntilDone:NO];
}
@end

I hope now you will get complete idea about multithreding  in iphone.

Output:

DownLoad Source Code from Here