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