多线程 GCD队列组

//  DYFViewController.m
//  623-08-队列组
//
//  Created by dyf on 14-6-23.
//  Copyright (c) 2014年 ___FULLUSERNAME___. All rights reserved.
//

#import "DYFViewController.h"

@interface DYFViewController ()
@property (weak, nonatomic ) IBOutlet UIImageView *iconV1;
@property (weak, nonatomic ) IBOutlet UIImageView *iconV2;
@property (weak, nonatomic ) IBOutlet UIImageView *bigIconV;

@end

@implementation DYFViewController

- ( 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
{
    NSLog (@ "%@" , [ NSThread currentThread]);
    dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    __block UIImage *icon1 = nil ;
    dispatch_group_async(group, queue, ^{
        NSLog (@ "%@" , [ NSThread currentThread]);
        //
        icon1 = [ self imageWithURL:@ "http://image.cache.xiu8.com/live/125/125/997729.jpg" ];

    });
    __block UIImage *icon2 = nil ;
    dispatch_group_async(group, queue, ^{
        NSLog (@ "%@" , [ NSThread currentThread]);
        //
        icon2 = [ self imageWithURL:@ "http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg" ];
    });

    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog (@ "%@" , [ NSThread currentThread]);
        //
        self .iconV1.image = icon1;
        self .iconV2.image = icon2;

        UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 100), NO , 0);
        [icon1 drawInRect:CGRectMake(0, 0, 100, 100)];
        [icon2 drawInRect:CGRectMake(100, 0, 100, 100)];
        self .bigIconV.image = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();
    });
}

- (UIImage *)imageWithURL:( NSString *)iconPath
{
    NSLog (@ "%@" , [ NSThread currentThread]);
    NSURL *url = [ NSURL URLWithString:iconPath];
    NSData *data = [ NSData dataWithContentsOfURL:url];
    return [UIImage imageWithData:data];
}

@end

 小结：

------------队列组------

1.有这么一种需求

·首先：分别异步执行2个耗时的操作

·其次：等2各异步操作都执行完毕后，再回到主线程执行操作

 

2.若想要快速高效的实现上述需求，可以考虑用队列组