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

   

转载于:https://www.cnblogs.com/Cheetah-yang/p/4664153.html