iOS 线程同步 加锁 @synchronized

#import "ViewController.h"
@interface ViewController ()
@property (nonatomic,assign)  int ticket;
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.ticket=50;
    [self ticketsTest];
    
    // Do any additional setup after loading the view.
}
-(void)saleTicket{
    @synchronized (self) {
        int ticket = self.ticket;
        sleep(.2);
        ticket--;
        self.ticket=ticket;
        NSLog(@"%d",self.ticket);
    }
}
-(void)ticketsTest{
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    dispatch_async(queue, ^{
        for (int i =0; i<5; i++) {
            [self saleTicket];
        }
    });
    dispatch_async(queue, ^{
        for (int i =0; i<5; i++) {
            [self saleTicket];
        }
    });
}

@end