[翻译] GCDObjC

GCDObjC

https://github.com/mjmsmith/gcdobjc

GCDObjC is an Objective-C wrapper for the most commonly used features of Grand Central Dispatch. It has four main aims:

GCDObjC 封装了GCD最常使用的一些特性，它有着如下的4点宗旨：

• Organize the flat C API into appropriate classes.
• Use intention-revealing names to distinguish between synchronous and asynchronous functions.
• Use more convenient arguments such as time intervals.
• Add convenience methods.
• 将C语言级别的API转换成合适的对象类型
• 使用见名知意的名字来区分同步和异步的方法
• 用更便利的参数，如时间间隔
• 添加一些便利的方法

Usage（使用）

GCDObjC requires ARC and iOS 6.0. (Prior to 6.0, dispatch objects were not considered Objective-C objects, and therefore required manual memory management.)

GCDObjC.h is the only header file that needs to be imported.

GCDObjC需要开启ARC以及iOS6.0（在6.0之前，dispatch对象不被当做Objective-C对象，所以需要手动管理内存）

GCDObjC.h是唯一需要包含的头文件。

For usage examples, see GCDObjCTests.m.

GCDQueue（GCD队列）

Queues are implemented in the GCDQueue class.

在GCDQueue类中实现了队列。

• convenience accessors for global queues
• 便利的系统相关队列

+ (GCDQueue *)mainQueue;
+ (GCDQueue *)globalQueue;
+ (GCDQueue *)highPriorityGlobalQueue;
+ (GCDQueue *)lowPriorityGlobalQueue;
+ (GCDQueue *)backgroundPriorityGlobalQueue;

• creating serial and concurrent queues
• 创建串行以及并发队列

- (instancetype)initSerial;
- (instancetype)initConcurrent;

• queueing blocks for asynchronous execution
• 队列的block用来执行异步操作

- (void)queueBlock:(dispatch_block_t)block;
- (void)queueBlock:(dispatch_block_t)block afterDelay:(double)seconds;
- (void)queueBlock:(dispatch_block_t)block inGroup:(GCDGroup *)group;

• queueing blocks for synchronous execution
• 队列的block用来执行同步操作

- (void)queueAndAwaitBlock:(dispatch_block_t)block;
- (void)queueAndAwaitBlock:(void (^)(size_t))block iterationCount:(size_t)count;

• queueing barrier blocks for synchronous or asynchronous execution
• 队列阻塞block用来执行同步或者异步操作

- (void)queueBarrierBlock:(dispatch_block_t)block;
- (void)queueAndAwaitBarrierBlock:(dispatch_block_t)block;

• queueing notify blocks on groups
• 用来监测groups的队列

- (void)queueNotifyBlock:(dispatch_block_t)block inGroup:(GCDGroup *)group;

• suspending and resuming a queue
• 挂起以及回复一个队列

- (void)suspend;
- (void)resume;

GCDSemaphore（GCD信号量）

Semaphores are implemented in the GCDSemaphore class.

GCDSemaphore类实现了信号量

• creating semaphores
• 创建信号量

- (instancetype)init;
- (instancetype)initWithValue:(long)value;

• signaling and waiting on a semaphore
• 发送以及等待一个信号量

- (BOOL)signal;
- (void)wait;
- (BOOL)wait:(double)seconds;

GCDGroup（GCD线程组）

Groups are implemented in the GCDGroup class.

GCDGroup实现了线程组。

• creating groups
• 创建组

- (instancetype)init;

• entering and leaving a group
• 加入以及脱离一个组

- (void)enter;
- (void)leave;

• waiting on completion of a group
• 等待一个线程组执行完毕

- (void)wait;
- (BOOL)wait:(double)seconds;

Macros（宏函数）

Two macros are provided for wrapping dispatch_once() calls.

给dispatch_once()调用提供了两个宏。

• executing a block only once: GCDExecOnce(block)
• 仅仅执行一次

for (int i = 0; i < 10; ++i) {
    GCDExecOnce(^{ NSLog(@"This will only be logged once."); });
}

• creating a singleton instance of a class: GCDSharedInstance(block)
• 创建一个类的单例

+ (instancetype)sharedInstance {
  GCDSharedInstance(^{ return [[self class] new]; });
}

The block supplied to GCDSharedInstance() must return an instance of the desired class.

GCDShardInstance()必须返回这个类的一个实例对象。

------------------------------------------------------------------------------------------------------

此类仅仅支持arc,所以是在arc环境下测试,简单易用,以测了所有的情况

------------------------------------------------------------------------------------------------------

串行主线程池

    [[GCDQueue mainQueue] queueBlock:^{
        NSLog(@"1");
    }];

    [[GCDQueue mainQueue] queueBlock:^{
        NSLog(@"2");
    }];
    
    [[GCDQueue mainQueue] queueBlock:^{
        NSLog(@"3");
    }];
    
    [[GCDQueue mainQueue] queueBlock:^{
        NSLog(@"4");
    }];

2014-04-09 10:39:57.210 StudyGCD_new[10395:60b] 1
2014-04-09 10:39:57.210 StudyGCD_new[10395:60b] 2
2014-04-09 10:39:57.211 StudyGCD_new[10395:60b] 3
2014-04-09 10:39:57.211 StudyGCD_new[10395:60b] 4

串行主线程池与并发主线程池混用

    [[GCDQueue globalQueue] queueBlock:^{
        // 系统并发线程池
        // ... 处理阻塞操作
        
        [[GCDQueue mainQueue] queueBlock:^{
            // 系统串行主线程池
            // ... 更新UI操作
        }];
    }];

自己创建的并发线程池

    GCDQueue *concurrentQueue = [[GCDQueue alloc] initConcurrent];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"1");
    }];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"2");
    }];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"3");
    }];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"4");
    }];

2014-04-09 11:08:39.450 StudyGCD_new[10592:1303] 1
2014-04-09 11:08:39.450 StudyGCD_new[10592:3903] 4
2014-04-09 11:08:39.450 StudyGCD_new[10592:3807] 2
2014-04-09 11:08:39.450 StudyGCD_new[10592:3707] 3

自己创建的串行线程池

    GCDQueue *serialQueue = [[GCDQueue alloc] initSerial];
    
    [serialQueue queueBlock:^{
        NSLog(@"1");
    }];
    
    [serialQueue queueBlock:^{
        NSLog(@"2");
    }];
    
    [serialQueue queueBlock:^{
        NSLog(@"3");
    }];
    
    [serialQueue queueBlock:^{
        NSLog(@"4");
    }];

2014-04-09 11:08:39.450 StudyGCD_new[10592:1303] 1
2014-04-09 11:08:39.450 StudyGCD_new[10592:3903] 2
2014-04-09 11:08:39.450 StudyGCD_new[10592:3807] 3
2014-04-09 11:08:39.450 StudyGCD_new[10592:3707] 4

主并发线程池延时1s执行

    NSLog(@"1");
    
    [[GCDQueue globalQueue] queueBlock:^{
        NSLog(@"Y.X.");
    } afterDelay:1.f];
    
    NSLog(@"2");

2014-04-09 11:11:46.349 StudyGCD_new[10640:1303] 1
2014-04-09 11:11:46.350 StudyGCD_new[10640:1303] 2
2014-04-09 11:11:47.350 StudyGCD_new[10640:1303] Y.X.

并发线程池中运行阻塞线程(queueAndAwaitBlock-dispatch_sync)

    GCDQueue *concurrentQueue = [[GCDQueue alloc] initConcurrent];
    
    [concurrentQueue queueAndAwaitBlock:^{
        sleep(1);
        NSLog(@"1");
    }];
    
    [concurrentQueue queueAndAwaitBlock:^{
        sleep(1);
        NSLog(@"2");
    }];
    
    [concurrentQueue queueAndAwaitBlock:^{
        sleep(1);
        NSLog(@"3");
    }];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"4");
    }];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"5");
    }];
    
    [concurrentQueue queueAndAwaitBlock:^{
        sleep(1);
        NSLog(@"6");
    }];

2014-04-09 11:21:15.186 StudyGCD_new[10946:60b] 1
2014-04-09 11:21:16.188 StudyGCD_new[10946:60b] 2
2014-04-09 11:21:17.190 StudyGCD_new[10946:60b] 3
2014-04-09 11:21:17.191 StudyGCD_new[10946:3807] 5
2014-04-09 11:21:17.191 StudyGCD_new[10946:1303] 4
2014-04-09 11:21:18.192 StudyGCD_new[10946:60b] 6

并发线程池,等待执行多次完毕后接着往下执行(dispatch_apply)

    GCDQueue *concurrentQueue = [[GCDQueue alloc] initConcurrent];
    
    NSLog(@"1-1-1");
    
    [concurrentQueue queueAndAwaitBlock:^(size_t count) {
        NSLog(@"%zu", count);
    } iterationCount:4];
    
    NSLog(@"2-2-2");

2014-04-09 11:27:39.400 StudyGCD_new[11131:60b] 1-1-1
2014-04-09 11:27:39.401 StudyGCD_new[11131:60b] 1
2014-04-09 11:27:39.401 StudyGCD_new[11131:1303] 0
2014-04-09 11:27:39.401 StudyGCD_new[11131:3707] 2
2014-04-09 11:27:39.401 StudyGCD_new[11131:3903] 3
2014-04-09 11:27:39.403 StudyGCD_new[11131:60b] 2-2-2

并发线程池,设置障碍线程而按照队列的形式执行(dispatch_barrier_async)

    GCDQueue *concurrentQueue = [[GCDQueue alloc] initConcurrent];
    
    [concurrentQueue queueBarrierBlock:^{
        NSLog(@"1");
        sleep(1);
    }];
    
    [concurrentQueue queueBarrierBlock:^{
        NSLog(@"2");
        sleep(1);
    }];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"Y.X.");
        sleep(1);
    }];
    
    [concurrentQueue queueBarrierBlock:^{
        NSLog(@"3");
        sleep(1);
    }];
    
    [concurrentQueue queueBarrierBlock:^{
        NSLog(@"4");
        sleep(1);
    }];

2014-04-09 11:33:08.190 StudyGCD_new[11252:1303] 1
2014-04-09 11:33:09.192 StudyGCD_new[11252:1303] 2
2014-04-09 11:33:10.194 StudyGCD_new[11252:1303] Y.X.
2014-04-09 11:33:11.196 StudyGCD_new[11252:1303] 3
2014-04-09 11:33:12.198 StudyGCD_new[11252:1303] 4

线程组以及监听

    GCDQueue *concurrentQueue = [[GCDQueue alloc] initConcurrent];
    GCDGroup *group = [[GCDGroup alloc] init];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"1");
    } inGroup:group];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"2");
    } inGroup:group];
    
    [concurrentQueue queueBlock:^{
        NSLog(@"3");
    } inGroup:group];
    
    [concurrentQueue queueNotifyBlock:^{
        NSLog(@"监测所有这个组中的子线程完成后执行此打印语句");
    } inGroup:group];

2014-04-09 11:37:19.492 StudyGCD_new[11343:3707] 3
2014-04-09 11:37:19.492 StudyGCD_new[11343:3807] 2
2014-04-09 11:37:19.492 StudyGCD_new[11343:1303] 1
2014-04-09 11:37:19.493 StudyGCD_new[11343:3807] 监测所有这个组中的子线程完成后执行此打印语句

先讲解系统的dispatch_group_enter来等待所有的异步操作结束后再执行最后的block

    // 创建一个组
    dispatch_group_t group = dispatch_group_create();

    /*
     dispatch_group_enter()
     
     * A call to this function must be balanced with a call to dispatch_group_leave.
     * 调用了这个方法就必须使用dispatch_group_leave来达到平衡
     */

    // 明确的标记一个block进入了一个组
    dispatch_group_enter(group);
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
        NSLog(@"1 starting");
        sleep(1);
        NSLog(@"1 complete");
        
        // 明确的标记一个这个组中的block已经完成
        dispatch_group_leave(group);
    });
    
    // 明确的标记一个block进入了一个组
    dispatch_group_enter(group);
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
        NSLog(@"2 starting");
        sleep(4);
        NSLog(@"2 complete");
        
        // 明确的标记一个这个组中的block已经完成
        dispatch_group_leave(group);
    });
    
    dispatch_async(dispatch_get_main_queue(), ^{
        // 同步等待之前提交的block任务都完成了才会执行这里
        dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
        NSLog(@"所有的进入group的都结束了,结束");
    });

2014-04-09 13:10:32.518 StudyGCD_new[11864:1303] 1 starting
2014-04-09 13:10:32.518 StudyGCD_new[11864:3403] 2 starting
2014-04-09 13:10:33.520 StudyGCD_new[11864:1303] 1 complete
2014-04-09 13:10:36.521 StudyGCD_new[11864:3403] 2 complete
2014-04-09 13:10:36.522 StudyGCD_new[11864:60b] 所有的进入group的都结束了,结束

GCDGroup同步并发线程,更精简

    GCDGroup *group = [[GCDGroup alloc] init];
    
    [group enter];
    [[GCDQueue globalQueue] queueBlock:^{
        sleep(2);
        NSLog(@"1结束");
        [group leave];
    }];
    
    [group enter];
    [[GCDQueue globalQueue] queueBlock:^{
        sleep(3);
        NSLog(@"2结束");
        [group leave];
    }];
    
    [[GCDQueue globalQueue] queueBlock:^{
        [group wait];
        NSLog(@"1.2都执行结束了,进来了这里");
    }];

2014-04-09 13:16:17.584 StudyGCD_new[11945:1303] 1结束
2014-04-09 13:16:18.584 StudyGCD_new[11945:3807] 2结束
2014-04-09 13:16:18.585 StudyGCD_new[11945:3707] 1.2都执行结束了,进来了这里

使用系统的信号量操作

    // 创建信号量
    dispatch_semaphore_t sem = dispatch_semaphore_create(0);
    
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
        NSLog(@"1开始");
        
        // 模拟阻塞操作
        sleep(2);
        NSLog(@"1结束");
        
        // 增加信号量
        dispatch_semaphore_signal(sem);
        
        sleep(1);
        dispatch_semaphore_signal(sem);
        
        sleep(1);
        dispatch_semaphore_signal(sem);
        
        sleep(1);
        dispatch_semaphore_signal(sem);
    });
    
    NSLog(@"阻塞吗?");
    // 减少信号量
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    NSLog(@"阻塞了1!");

    // 减少信号量
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    NSLog(@"阻塞了2!");
    
    // 减少信号量
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    NSLog(@"阻塞了3!");
    
    // 减少信号量
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    NSLog(@"阻塞了4!");

2014-04-09 13:31:10.135 StudyGCD_new[12198:1303] 1开始

2014-04-09 13:31:10.134 StudyGCD_new[12198:60b] 阻塞吗?

2014-04-09 13:31:12.137 StudyGCD_new[12198:1303] 1结束

2014-04-09 13:31:12.138 StudyGCD_new[12198:60b] 阻塞了1!

2014-04-09 13:31:13.139 StudyGCD_new[12198:60b] 阻塞了2!

2014-04-09 13:31:14.140 StudyGCD_new[12198:60b] 阻塞了3!

2014-04-09 13:31:15.141 StudyGCD_new[12198:60b] 阻塞了4!

信号量操作

    GCDSemaphore *semaphore = [[GCDSemaphore alloc] initWithValue:0];
    
    [[GCDQueue globalQueue] queueBlock:^{
        sleep(4);
        [semaphore signal];
    }];
    
    [semaphore wait];
    NSLog(@"结束");

2014-04-09 13:39:09.476 StudyGCD_new[12298:60b] 结束