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```objc

import "ViewController.h"

@interface ViewController () @property (weak, nonatomic) IBOutlet UIActivityIndicatorView *action;

@end

@implementation ViewController

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

//模拟从服务器上获取数据（返回字符串) -(NSString *)loadingSomeThingFromServer { [NSThread sleepForTimeInterval:2];

return @"Hello wangdelong";

}

// 将传入参数全部转换成大写字母 -(NSString *)changname:(NSString *)result { [NSThread setThreadPriority:2];

return  [result uppercaseString];

}

//模拟从服务器上第一次处理数据（将从服务器上返回的字符串长度转换成字符串：（Number of chars: ) -(NSString *)dealTheResult:(NSString *)result { [NSThread sleepForTimeInterval:3];

return [NSString stringWithFormat:@"long of zhe thinge is :%d",result.length];

}

//模拟第二次处理服务器上的数据，将返回的字符串里的小的w转换成大写的W -(NSString *)dealTheNewThings:(NSString *)result { [NSThread sleepForTimeInterval:3];

return [result stringByReplacingOccurrencesOfString:@"W" withString:@"w"];

}

• (IBAction)doSomething:(UIButton *)sender {

// 声明一个表示时间的对象，[NSDate date]获取的是当前时间 NSDate *startTime = [NSDate date];

[self.action startAnimating];

// 创建一个队列，使其实现并发－－－－－原以为能实现风火轮的准时停止，但是 dispatchqueuet queue = dispatchgetglobalqueue(DISPATCHQUEUEPRIORITYDEFAULT, 0);

// 异步发布 dispatch_async(queue, ^{

// //从服务器上取数据 __block NSString *result = nil;

    dispatch_async(queue, ^{

// 处理事件

        result = [self loadingSomeThingFromServer];

        NSLog(@"********输入的是:%@",result);


        });


        result = [self changname:result];
    //    第一次处理数据
        NSString *second = [self dealTheResult:result];
    //    第二次处理数据
        NSString *third = [self dealTheNewThings:result];

        NSLog(@"********大写的是:%@",result);
        NSLog(@"********:%@",second);
        NSLog(@"********修改后的是:%@",third);

        NSDate *endTime = [NSDate date];

        NSLog(@"共经过 %f m时间",[endTime  timeIntervalSinceDate:startTime ]);

        dispatch_sync(dispatch_get_main_queue(), ^{
            [self.action stopAnimating];
        });

});

}

//新添加的方法，显示最后的结果 -(void)showTheLastResult:(NSString *)first Second:(NSString *)second { NSLog(@"[First:]%@,[Second:]%@",first,second);

}

• (IBAction)doNewThing:(UIButton *)sender {

// 声明一个表示时间的对象，[NSDate date]获取的是当前时间 NSDate *startTime = [NSDate date]; [self.action startAnimating];

dispatch_queue_t queue =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

// 异步分发队列 dispatch_async(queue, ^{

    NSString *result =[self loadingSomeThingFromServer];

    NSString *changName = [self changname:result];

    NSLog(@"********输入的是:%@",result);

    NSLog(@"********大写的是:%@",changName);

// GCD提供了dispatch group，可以将一组任务集合在一起，等待这组任务完成后再继续， dispatchgroupt group =dispatchgroupcreate();

// __block这里是block的用法，为了能让block能传参数

    __block  NSString * first ;

    __block NSString * second;

    dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{


        first = [self dealTheResult:changName];
        NSLog(@"********:%@",first);

    });

    dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{


        second = [self dealTheNewThings:changName];

        NSLog(@"********修改后的是:%@",second);
    });

    dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        [self showTheLastResult:first Second:second];


        dispatch_sync(dispatch_get_main_queue(), ^{
            [self.action stopAnimating];
        });


        NSLog(@"共经过 %f m时间",[[NSDate date] timeIntervalSinceDate:startTime]);

    });


});

}

@end

```

GCD(2),布布扣,bubuko.com

GCD(2)

标签：os   数据   art   io   for   cti   

原文地址：http://www.cnblogs.com/wangdelong/p/3852812.html