iOS-GCD多线程编程详解2 






iOS-GCD多线程编程详解2







一.前言


上一篇文章中简单的使用了GCD的多线程编程和有名的队列，今天将要讨论的是dispatch_apply函数的使用；


二.dispatch_apply说明







void dispatch_apply(size_t iterations,
dispatch_queue_t queue,void (^block)(size_t));


该函数的主要作用是提交一个block到队列中多次执行，执行的次数由iterations决定，block中可以通过传递的参数知道是第几次执行索引，如果把它提交到一个并发队列中它就会并发执行，执行的顺序并不是按照索引决定的，所以在应用带函数对相同数据进行修改时要注意数据的完整性


参数：1.size_t  iterations:block多次执行次数


   2.queue:block提交的队列


   3.void (^block)(size_t) ：block实体


三.详细使用


1.把block提交到主队列




   


         dispatch_apply(5, dispatch_get_main_queue(), ^(size_t i) {
                 NSLog(@"我是第%ld次执行，我运行在线程%@",i,[NSThread currentThread]);
   	 });
 



运行结果是没有东西输出，屏幕卡死




2.把block交到global队列




<span style="white-space:pre">	</span>dispatch_apply(5, dispatch_get_global_queue(0, 0), ^(size_t i) {
      <span style="white-space:pre">	</span>  NSLog(@"我是第%ld次执行，我运行在线程%@",i,[NSThread currentThread]);
   <span style="white-space:pre">	</span> });





运行结果：


第一次：




2015-01-05 23:12:07.367 GCDTest[716:38747]
我是第1次执行，我运行在线程<NSThread: 0x7fa2fa70d010>{number = 2, name = (null)}


2015-01-05 23:12:07.367 GCDTest[716:38703]
我是第0次执行，我运行在线程<NSThread: 0x7fa2fa40f930>{number = 1, name = main}


2015-01-05 23:12:07.367 GCDTest[716:38744]
我是第3次执行，我运行在线程<NSThread: 0x7fa2fa422940>{number = 3, name = (null)}


2015-01-05 23:12:07.367 GCDTest[716:38746]
我是第2次执行，我运行在线程<NSThread: 0x7fa2fa619cc0>{number = 4, name = (null)}


2015-01-05 23:12:07.368 GCDTest[716:38747]
我是第4次执行，我运行在线程<NSThread: 0x7fa2fa70d010>{number = 2, name = (null)}


第二次：




2015-01-05 23:13:04.578 GCDTest[726:39129]
我是第0次执行，我运行在线程<NSThread: 0x7fd3d25282c0>{number = 1, name = main}


2015-01-05 23:13:04.579 GCDTest[726:39129]
我是第4次执行，我运行在线程<NSThread: 0x7fd3d25282c0>{number = 1, name = main}


2015-01-05 23:13:04.578 GCDTest[726:39161]
我是第1次执行，我运行在线程<NSThread: 0x7fd3d24212e0>{number = 2, name = (null)}


2015-01-05 23:13:04.578 GCDTest[726:39163]
我是第2次执行，我运行在线程<NSThread: 0x7fd3d255f220>{number = 4, name = (null)}




2015-01-05 23:13:04.578 GCDTest[726:39164]
我是第3次执行，我运行在线程<NSThread: 0x7fd3d2537850>{number = 3, name = (null)}




第三次：


2015-01-05 23:13:50.186 GCDTest[731:39567]
我是第3次执行，我运行在线程<NSThread: 0x7fa113e14230>{number = 3, name = (null)}






2015-01-05 23:13:50.186 GCDTest[731:39567]
我是第4次执行，我运行在线程<NSThread: 0x7fa113e14230>{number = 3, name = (null)}


2015-01-05 23:13:50.186 GCDTest[731:39529]
我是第0次执行，我运行在线程<NSThread: 0x7fa113e135b0>{number = 1, name = main}


2015-01-05 23:13:50.186 GCDTest[731:39564]
我是第2次执行，我运行在线程<NSThread: 0x7fa113c10910>{number = 4, name = (null)}


2015-01-05 23:13:50.186 GCDTest[731:39566]
我是第1次执行，我运行在线程<NSThread: 0x7fa113f28390>{number = 2, name = (null)}

结果分析：三次运行中第一次运行的都在主线程，其余的都在非主线程，执行顺序是随机的，就可以猜想为什么在主队列会造成屏幕卡死，因为第一次调用是在主线程造成死锁。






3.把block提交到自定义系列队列中


<span style="white-space:pre">	</span>dispatch_queue_t customerQueue = dispatch_queue_create("", DISPATCH_QUEUE_SERIAL);
  <span style="white-space:pre">	</span>  dispatch_apply(5, customerQueue, ^(size_t i) {
       <span style="white-space:pre">		</span> NSLog(@"我是第%ld次执行，我运行在线程%@",i,[NSThread currentThread]);
   <span style="white-space:pre">	</span> });










运行结果：在主线程中调用的结果




2015-01-05 23:21:34.973 GCDTest[760:41219]
我是第0次执行，我运行在线程<NSThread: 0x7fb3084283c0>{number = 1, name = main}


2015-01-05 23:21:34.974 GCDTest[760:41219]
我是第1次执行，我运行在线程<NSThread: 0x7fb3084283c0>{number = 1, name = main}


2015-01-05 23:21:34.974 GCDTest[760:41219]
我是第2次执行，我运行在线程<NSThread: 0x7fb3084283c0>{number = 1, name = main}


2015-01-05 23:21:34.974 GCDTest[760:41219]
我是第3次执行，我运行在线程<NSThread: 0x7fb3084283c0>{number = 1, name = main}


2015-01-05 23:21:34.974 GCDTest[760:41219]
我是第4次执行，我运行在线程<NSThread: 0x7fb3084283c0>{number = 1, name = main}

顺序执行并在主线程中执行，



运行结果：在子线程中的调用







-(void)netThread:(id)sender{
    dispatch_queue_t customerQueue = dispatch_queue_create("", DISPATCH_QUEUE_SERIAL);
    dispatch_apply(5, customerQueue, ^(size_t i) {
        NSLog(@"我是第%ld次执行，我运行在线程%@",i,[NSThread currentThread]);
    });
}







2015-01-05 23:25:26.386 GCDTest[844:42550]
我是第0次执行，我运行在线程<NSThread: 0x7f9802684290>{number = 2, name = (null)}


2015-01-05 23:25:26.387 GCDTest[844:42550]
我是第1次执行，我运行在线程<NSThread: 0x7f9802684290>{number = 2, name = (null)}


2015-01-05 23:25:26.387 GCDTest[844:42550]
我是第2次执行，我运行在线程<NSThread: 0x7f9802684290>{number = 2, name = (null)}


2015-01-05 23:25:26.387 GCDTest[844:42550]
我是第3次执行，我运行在线程<NSThread: 0x7f9802684290>{number = 2, name = (null)}


2015-01-05 23:25:26.387 GCDTest[844:42550]
我是第4次执行，我运行在线程<NSThread: 0x7f9802684290>{number = 2, name = (null)}

顺序执行，也是在同一个线程中执行





4.把block提交到自定义的并发队列




dispatch_queue_t customerQueue = dispatch_queue_create("", DISPATCH_QUEUE_CONCURRENT);
    dispatch_apply(5, customerQueue, ^(size_t i) {
        NSLog(@"我是第%ld次执行，我运行在线程%@",i,[NSThread currentThread]);
    });





运行结果：在主线程中调用的结果


第一次：




2015-01-05 23:29:45.326 GCDTest[870:44074]
我是第1次执行，我运行在线程<NSThread: 0x7f9a0b724d00>{number = 2, name = (null)}


2015-01-05 23:29:45.326 GCDTest[870:44075]
我是第2次执行，我运行在线程<NSThread: 0x7f9a0b72b7a0>{number = 4, name = (null)}


2015-01-05 23:29:45.326 GCDTest[870:44077]
我是第3次执行，我运行在线程<NSThread: 0x7f9a0b5841c0>{number = 3, name = (null)}


2015-01-05 23:29:45.326 GCDTest[870:44034]
我是第0次执行，我运行在线程<NSThread: 0x7f9a0b528ac0>{number = 1, name = main}


2015-01-05 23:29:45.327 GCDTest[870:44074]
我是第4次执行，我运行在线程<NSThread: 0x7f9a0b724d00>{number = 2, name = (null)}




第二次：




2015-01-05 23:31:06.273 GCDTest[881:44838]
我是第0次执行，我运行在线程<NSThread: 0x7fdd78f13a70>{number = 1, name = main}


2015-01-05 23:31:06.274 GCDTest[881:44838]
我是第4次执行，我运行在线程<NSThread: 0x7fdd78f13a70>{number = 1, name = main}


2015-01-05 23:31:06.273 GCDTest[881:44903]
我是第3次执行，我运行在线程<NSThread: 0x7fdd78f99fc0>{number = 4, name = (null)}


2015-01-05 23:31:06.273 GCDTest[881:44901]
我是第1次执行，我运行在线程<NSThread: 0x7fdd78e218a0>{number = 2, name = (null)}


2015-01-05 23:31:06.273 GCDTest[881:44902]
我是第2次执行，我运行在线程<NSThread: 0x7fdd78d17640>{number = 3, name = (null)}

第三次：



2015-01-05 23:31:57.463 GCDTest[886:45383]
我是第2次执行，我运行在线程<NSThread: 0x7fa040d08370>{number = 4, name = (null)}


2015-01-05 23:31:57.463 GCDTest[886:45385]
我是第1次执行，我运行在线程<NSThread: 0x7fa040c2c510>{number = 3, name = (null)}


2015-01-05 23:31:57.463 GCDTest[886:45386]
我是第0次执行，我运行在线程<NSThread: 0x7fa040f16c20>{number = 2, name = (null)}


2015-01-05 23:31:57.463 GCDTest[886:45330]
我是第3次执行，我运行在线程<NSThread: 0x7fa040c291b0>{number = 1, name = main}


2015-01-05 23:31:57.464 GCDTest[886:45383]
我是第4次执行，我运行在线程<NSThread: 0x7fa040d08370>{number = 4, name = (null)}



说明block被提交的线程是随机的并没有规定那个线程执行




-(void)netThread:(id)sender{
    dispatch_queue_t customerQueue = dispatch_queue_create("", DISPATCH_QUEUE_CONCURRENT);
    dispatch_apply(5, customerQueue, ^(size_t i) {
        NSLog(@"我是第%ld次执行，我运行在线程%@",i,[NSThread currentThread]);
    });
}


运行结果：在子线程中调用的结果









2015-01-05 23:33:22.767 GCDTest[910:46193]
我是第0次执行，我运行在线程<NSThread: 0x7f93e1e248c0>{number = 2, name = (null)}


2015-01-05 23:33:22.767 GCDTest[910:46188]
我是第3次执行，我运行在线程<NSThread: 0x7f93e1c1ce90>{number = 4, name = (null)}


2015-01-05 23:33:22.767 GCDTest[910:46190]
我是第1次执行，我运行在线程<NSThread: 0x7f93e1c1c010>{number = 3, name = (null)}


2015-01-05 23:33:22.768 GCDTest[910:46188]
我是第4次执行，我运行在线程<NSThread: 0x7f93e1c1ce90>{number = 4, name = (null)}


2015-01-05 23:33:22.767 GCDTest[910:46189]
我是第2次执行，我运行在线程<NSThread: 0x7f93e1e33fb0>{number = 5, name = (null)}

结果分析：多次结果都是随机的顺序，随机的线程













四.小结


dispatch_apply:要注意的问题是屏幕卡死的情况和对数据修改的完整性和正确性。




























            

            
posted @ 
2015-01-05 22:50 
fineman 
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