IOS_GCD使用

//
//  PJViewController.m
//  队列
//
//  Created by pj on 14-8-2.
//  Copyright (c) 2014年 pj. All rights reserved.
//

#import "PJViewController.h"

@interface PJViewController ()

@end

@implementation PJViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self demo4];
}

// 主队列
- (void)demo4
{
    // 1.获取主队列
    dispatch_queue_t q = dispatch_get_main_queue();
    // 2.添加异步任务，这里会开1条线程,因为他是在主队列里面的
    for (int i = 0; i < 100; i++) {
        dispatch_async(q, ^{
            NSLog(@"%@",[NSThread currentThread]);
        });
    }
    
    // 这个是死锁，因为他会等到主线程执行完毕后,才会执行这个方法,所以会是死锁
    dispatch_sync(q, ^{
        NSLog(@"%@",[NSThread currentThread]);
    });
    
    
}

// 全局并行队列
- (void)demo3
{
    // 1.获取全局队列
    dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    // 2.添加异步任务，这里会开N条线程,因为他是在并行队列里面的
        for (int i = 0; i < 100; i++) {
            dispatch_async(q, ^{
                NSLog(@"%@",[NSThread currentThread]);
            });
        }
 
}

- (void)demo2
{
    // 1.创建并行队列,能开N条线程
    dispatch_queue_t q = dispatch_queue_create("myqueue", DISPATCH_QUEUE_CONCURRENT);
    // 2.添加异步任务，这里会开N条线程,因为他是在并行队列里面的
//    for (int i = 0; i < 100; i++) {
//        dispatch_async(q, ^{
//            NSLog(@"%@",[NSThread currentThread]);
//        });
//    }
    // 3.添加同步任务，同步任务是在主线程上执行,不会开启新的线程
    for (int i = 0; i < 100; i++) {
        dispatch_sync(q, ^{
            NSLog(@"%@",[NSThread currentThread]);
        });
    }
}


- (void)demo1
{
    // 1.创建串行队列,只能开一条线程
    dispatch_queue_t q = dispatch_queue_create("myqueue", DISPATCH_QUEUE_SERIAL);
    // 2.添加任务
    // 他只会在一个异步线程执行
    for (int i = 0; i < 100; i++) {
        dispatch_async(q, ^{
            NSLog(@"%@",[NSThread currentThread]);
        });
    }
}

@end