考察点：

  • NSLock锁运用
  • 异步转同步
  • 并发队列

启动三个线程A，B，C，打印10次 按照ABC的顺序输出

  1. dispatch_queue_t queueA = dispatch_queue_create("queuea", DISPATCH_QUEUE_CONCURRENT);
  2.     dispatch_async(queueA, ^{
  3.         for (int i = 0; i<10; i++) {
  4.             NSLog(@"A======= %@",@(i));
  5.         }
  6.     });
  8.     dispatch_queue_t queueB = dispatch_queue_create("queueb", DISPATCH_QUEUE_CONCURRENT);
  9.     dispatch_async(queueB, ^{
  10.         for (int i = 0; i<10; i++) {
  11.              NSLog(@"B======= %@",@(i));
  12.         }
  13.     });
  15.     dispatch_queue_t queueC = dispatch_queue_create("queuec", DISPATCH_QUEUE_CONCURRENT);
  16.     dispatch_async(queueC, ^{
  17.         for (int i = 0; i<10; i++) {
  18.              NSLog(@"C======= %@",@(i));
  19.              NSLog(@"   ");
  20.         }
  21.     });

利用NSLock实现

  2.     NSLock *lockA = [[NSLock alloc] init];
  3.     NSLock *lockB = [[NSLock alloc] init];
  4.     NSLock *lockC = [[NSLock alloc] init];
  6.     [lockB lock];
  7.     [lockC lock];
  9.     dispatch_queue_t queueA = dispatch_queue_create("queuea", DISPATCH_QUEUE_CONCURRENT);
  10.     dispatch_async(queueA, ^{
  11.         for (int i = 0; i<10; i++) {
  12.             [lockA lock];
  13.             NSLog(@"A======= %@",@(i));
  14.             [lockB unlock];
  15.         }
  16.     });
  18.     dispatch_queue_t queueB = dispatch_queue_create("queueb", DISPATCH_QUEUE_CONCURRENT);
  19.     dispatch_async(queueB, ^{
  20.         for (int i = 0; i<10; i++) {
  21.             [lockB lock];
  22.              NSLog(@"B======= %@",@(i));
  23.             [lockC unlock];
  24.         }
  25.     });
  27.     dispatch_queue_t queueC = dispatch_queue_create("queuec", DISPATCH_QUEUE_CONCURRENT);
  28.     dispatch_async(queueC, ^{
  29.         for (int i = 0; i<10; i++) {
  30.             [lockC lock];
  31.              NSLog(@"C======= %@",@(i));
  32.              NSLog(@"   ");
  33.             [lockA unlock];
  34.         }
  35.     });
  38. 2019-06-20 01:06:23.384170+0800 xxtest[2808:669702] A======= 0
  39. 2019-06-20 01:06:23.384379+0800 xxtest[2808:669701] B======= 0
  40. 2019-06-20 01:06:23.384515+0800 xxtest[2808:669703] C======= 0
  41. 2019-06-20 01:06:23.384613+0800 xxtest[2808:669703] 
  42. 2019-06-20 01:06:23.384750+0800 xxtest[2808:669702] A======= 1
  43. 2019-06-20 01:06:23.384878+0800 xxtest[2808:669701] B======= 1
  44. 2019-06-20 01:06:23.384992+0800 xxtest[2808:669703] C======= 1
  45. 2019-06-20 01:06:23.385716+0800 xxtest[2808:669703] 
  46. 2019-06-20 01:06:23.386194+0800 xxtest[2808:669702] A======= 2
  47. 2019-06-20 01:06:23.386590+0800 xxtest[2808:669701] B======= 2
  48. 2019-06-20 01:06:23.387100+0800 xxtest[2808:669703] C======= 2
  49. 2019-06-20 01:06:23.387497+0800 xxtest[2808:669703] 
  50. 2019-06-20 01:06:23.387857+0800 xxtest[2808:669702] A======= 3
  51. 2019-06-20 01:06:23.388317+0800 xxtest[2808:669701] B======= 3
  52. 2019-06-20 01:06:23.388663+0800 xxtest[2808:669703] C======= 3
  53. 2019-06-20 01:06:23.388969+0800 xxtest[2808:669703] 
  54. 2019-06-20 01:06:23.389857+0800 xxtest[2808:669702] A======= 4
  55. 2019-06-20 01:06:23.390137+0800 xxtest[2808:669701] B======= 4
  56. 2019-06-20 01:06:23.390546+0800 xxtest[2808:669703] C======= 4
  57. 2019-06-20 01:06:23.390847+0800 xxtest[2808:669703] 
  58. 2019-06-20 01:06:23.391203+0800 xxtest[2808:669702] A======= 5
  59. 2019-06-20 01:06:23.391476+0800 xxtest[2808:669701] B======= 5
  60. 2019-06-20 01:06:23.391854+0800 xxtest[2808:669703] C======= 5
  61. 2019-06-20 01:06:23.392134+0800 xxtest[2808:669703] 
  62. 2019-06-20 01:06:23.392443+0800 xxtest[2808:669702] A======= 6
  63. 2019-06-20 01:06:23.392804+0800 xxtest[2808:669701] B======= 6
  64. 2019-06-20 01:06:23.393107+0800 xxtest[2808:669703] C======= 6
  65. 2019-06-20 01:06:23.393413+0800 xxtest[2808:669703] 
  66. 2019-06-20 01:06:23.393685+0800 xxtest[2808:669702] A======= 7
  67. 2019-06-20 01:06:23.394006+0800 xxtest[2808:669701] B======= 7
  68. 2019-06-20 01:06:23.394301+0800 xxtest[2808:669703] C======= 7
  69. 2019-06-20 01:06:23.394578+0800 xxtest[2808:669703] 
  70. 2019-06-20 01:06:23.394959+0800 xxtest[2808:669702] A======= 8
  71. 2019-06-20 01:06:23.395532+0800 xxtest[2808:669701] B======= 8
  72. 2019-06-20 01:06:23.395873+0800 xxtest[2808:669703] C======= 8
  73. 2019-06-20 01:06:23.396117+0800 xxtest[2808:669703] 
  74. 2019-06-20 01:06:23.396508+0800 xxtest[2808:669702] A======= 9
  75. 2019-06-20 01:06:23.396897+0800 xxtest[2808:669701] B======= 9
  76. 2019-06-20 01:06:23.397307+0800 xxtest[2808:669703] C======= 9
  77. 2019-06-20 01:06:23.397649+0800 xxtest[2808:669703]

利用信号量实现

  1.  dispatch_semaphore_t semaA = dispatch_semaphore_create(1);
  2.     dispatch_semaphore_t semaB = dispatch_semaphore_create(0);
  3.     dispatch_semaphore_t semaC = dispatch_semaphore_create(0);
  6.     dispatch_queue_t queueA = dispatch_queue_create("queuea", DISPATCH_QUEUE_CONCURRENT);
  7.     dispatch_async(queueA, ^{
  8.         for (int i = 0; i<10; i++) {
  9.             dispatch_semaphore_wait(semaA, DISPATCH_TIME_FOREVER);
  10.             NSLog(@"A======= %@",@(i));
  11.             dispatch_semaphore_signal(semaB);
  12.         }
  13.     });
  15.     dispatch_queue_t queueB = dispatch_queue_create("queueb", DISPATCH_QUEUE_CONCURRENT);
  16.     dispatch_async(queueB, ^{
  17.         for (int i = 0; i<10; i++) {
  18.             dispatch_semaphore_wait(semaB, DISPATCH_TIME_FOREVER);
  19.             NSLog(@"B======= %@",@(i));
  20.             dispatch_semaphore_signal(semaC);
  21.         }
  22.     });
  24.     dispatch_queue_t queueC = dispatch_queue_create("queuec", DISPATCH_QUEUE_CONCURRENT);
  25.     dispatch_async(queueC, ^{
  26.         for (int i = 0; i<10; i++) {
  27.             dispatch_semaphore_wait(semaC, DISPATCH_TIME_FOREVER);
  28.             NSLog(@"C======= %@",@(i));
  29.             NSLog(@"   ");
  30.             dispatch_semaphore_signal(semaA);
  31.         }
  32.     });
  34. 2019-06-20 01:40:25.050013+0800 xxtest[2938:708288] A======= 0
  35. 2019-06-20 01:40:25.050183+0800 xxtest[2938:708285] B======= 0
  36. 2019-06-20 01:40:25.050297+0800 xxtest[2938:708286] C======= 0
  37. 2019-06-20 01:40:25.050391+0800 xxtest[2938:708286] 
  38. 2019-06-20 01:40:25.050487+0800 xxtest[2938:708288] A======= 1
  39. 2019-06-20 01:40:25.050588+0800 xxtest[2938:708285] B======= 1
  40. 2019-06-20 01:40:25.050684+0800 xxtest[2938:708286] C======= 1
  41. 2019-06-20 01:40:25.050782+0800 xxtest[2938:708286] 
  42. 2019-06-20 01:40:25.050881+0800 xxtest[2938:708288] A======= 2
  43. 2019-06-20 01:40:25.050982+0800 xxtest[2938:708285] B======= 2
  44. 2019-06-20 01:40:25.051442+0800 xxtest[2938:708286] C======= 2
  45. 2019-06-20 01:40:25.051695+0800 xxtest[2938:708286] 
  46. 2019-06-20 01:40:25.051928+0800 xxtest[2938:708288] A======= 3
  47. 2019-06-20 01:40:25.052162+0800 xxtest[2938:708285] B======= 3
  48. 2019-06-20 01:40:25.052414+0800 xxtest[2938:708286] C======= 3
  49. 2019-06-20 01:40:25.052841+0800 xxtest[2938:708286] 
  50. 2019-06-20 01:40:25.053073+0800 xxtest[2938:708288] A======= 4
  51. 2019-06-20 01:40:25.053340+0800 xxtest[2938:708285] B======= 4
  52. 2019-06-20 01:40:25.053617+0800 xxtest[2938:708286] C======= 4
  53. 2019-06-20 01:40:25.053843+0800 xxtest[2938:708286] 
  54. 2019-06-20 01:40:25.054094+0800 xxtest[2938:708288] A======= 5
  55. 2019-06-20 01:40:25.055448+0800 xxtest[2938:708285] B======= 5
  56. 2019-06-20 01:40:25.055584+0800 xxtest[2938:708286] C======= 5
  57. 2019-06-20 01:40:25.055757+0800 xxtest[2938:708286] 
  58. 2019-06-20 01:40:25.055888+0800 xxtest[2938:708288] A======= 6
  59. 2019-06-20 01:40:25.056116+0800 xxtest[2938:708285] B======= 6
  60. 2019-06-20 01:40:25.056455+0800 xxtest[2938:708286] C======= 6
  61. 2019-06-20 01:40:25.056871+0800 xxtest[2938:708286] 
  62. 2019-06-20 01:40:25.057176+0800 xxtest[2938:708288] A======= 7
  63. 2019-06-20 01:40:25.057484+0800 xxtest[2938:708285] B======= 7
  64. 2019-06-20 01:40:25.057789+0800 xxtest[2938:708286] C======= 7
  65. 2019-06-20 01:40:25.058204+0800 xxtest[2938:708286] 
  66. 2019-06-20 01:40:25.058479+0800 xxtest[2938:708288] A======= 8
  67. 2019-06-20 01:40:25.058947+0800 xxtest[2938:708285] B======= 8
  68. 2019-06-20 01:40:25.059211+0800 xxtest[2938:708286] C======= 8
  69. 2019-06-20 01:40:25.059469+0800 xxtest[2938:708286] 
  70. 2019-06-20 01:40:25.059701+0800 xxtest[2938:708288] A======= 9
  71. 2019-06-20 01:40:25.060025+0800 xxtest[2938:708285] B======= 9
  72. 2019-06-20 01:40:25.060360+0800 xxtest[2938:708286] C======= 9
  73. 2019-06-20 01:40:25.060585+0800 xxtest[2938:708286]