GCD 函数的那些任务

一、函数的任务

1、创建和管理队列

dispatch_get_global_queue

dispatch_get_main_queue

dispatch_queue_create

dispatch_get_current_queue

dispatch_queue_get_label

dispatch_set_target_queue

dispatch_main

2、队列任务分发

dispatch_async

dispatch_async_f

dispatch_sync

dispatch_sync_f

dispatch_after

dispatch_after_f

dispatch_apply

dispatch_apply_f

dispatch_once

3、使用分发组

dispatch_group_async

dispatch_group_async_f

dispatch_group_create

dispatch_group_enter

dispatch_group_leave

dispatch_group_notify

dispatch_group_notify_f

dispatch_group_wait

4、管理分发对象

dispatch_debug

dispatch_get_context

dispatch_release

dispatch_resume

dispatch_retain

dispatch_set_context

dispatch_set_finalizer_f

dispatch_suspend

5、Using Semaphores

dispatch_semaphore_create

dispatch_semaphore_signal

dispatch_semaphore_wait

6、Using Barriers

dispatch_barrier_async

dispatch_barrier_async_f

dispatch_barrier_sync

dispatch_barrier_sync_f

7、管理分发来源

dispatch_source_cancel

dispatch_source_create

dispatch_source_get_data

dispatch_source_get_handle

dispatch_source_get_mask

dispatch_source_merge_data

dispatch_source_set_registration_handler

dispatch_source_set_registration_handler_f

dispatch_source_set_cancel_handler

dispatch_source_set_cancel_handler_f

dispatch_source_set_event_handler

dispatch_source_set_event_handler_f

dispatch_source_set_timer

dispatch_source_testcancel

8、使用分发I / O便利的API

dispatch_read

dispatch_write

9、使用分发I / O通道API

dispatch_io_create

dispatch_io_create_with_path

dispatch_io_read

dispatch_io_write

dispatch_io_close

dispatch_io_set_high_water

dispatch_io_set_low_water

dispatch_io_set_interval

10、管理分发数据对象

dispatch_data_create

dispatch_data_get_size

dispatch_data_create_map

dispatch_data_create_concat

dispatch_data_create_subrange

dispatch_data_apply

dispatch_data_copy_region

11、管理时间

dispatch_time

dispatch_walltime

12、Managing Queue-Specific Context Data

dispatch_queue_set_specific

dispatch_queue_get_specific

dispatch_get_specific

二、函数

1、dispatch_after

//延迟2.0s执行

int64_t delayInSeconds = 2.0;

dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW,delayInSeconds *NSEC_PER_SEC);

dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

    //do something...

});

2、dispatch_apply

//    对于同步执行，这个函数调用单一block多次，并平行运算，然后等待所有运算结束。和数组循环有点类似

    dispatch_queue_t queue3 =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0);

    dispatch_apply([array count], queue3, ^(size_t index){

        [self doSomethingIntensiveWith:[arrayobjectAtIndex:index]];

    });

3、dispatch_async

//  全局队列中后台执行：

    dispatch_async(dispatch_get_global_queue(0,0), ^{

        // something

    });

4、dispatch_barrier_async

//    dispatch_barrier_async是在前面的任务执行结束后它才执行，而且它后面的任务等它执行完成之后才会执行

    dispatch_queue_t queue6 =dispatch_queue_create("gcdtest.zfl.demo",DISPATCH_QUEUE_CONCURRENT);

    dispatch_async(queue6, ^{

        [NSThread sleepForTimeInterval:2];

        NSLog(@"dispatch_async1");

    });

    dispatch_async(queue6, ^{

        NSLog(@"dispatch_async2");

    });

    dispatch_barrier_async(queue6, ^{

        NSLog(@"dispatch_barrier_async");      

    });

    dispatch_async(queue6, ^{

        NSLog(@"dispatch_async3");  

    });

5、dispatch_data_apply

//here is a function which transforms a data object containing ASCII data into an NSString using dispatch_data_apply to avoid unnecessary copies:

NSString *StringFromDispatchData(dispatch_data_t data)

{

    NSMutableString *s = [NSMutableStringstringWithCapacity:dispatch_data_get_size(data)];

    dispatch_data_apply(data, ^(dispatch_data_t region,size_t offset,const void *buffer, size_t size) {

        [s appendFormat: @"%.*s", size, buffer];

        return (_Bool)true;

    });

    return s;

}

6、dispatch_get_global_queue

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0); //获取全局队列

7、dispatch_get_main_queue

dispatch_get_main_queue(); //获取主队列

8、dispatch_queue_create

dispatch_queue_t queue = dispatch_queue_create("blog.devtang.com",NULL); //创建一个队列

9、dispatch_group_wait

//    一个dispatch group可以用来将多个block组成一组以监测这些Block全部完成或者等待全部完成时发出的消息。使用函数dispatch_group_create来创建，然后使用函数dispatch_group_async来将block提交至一个dispatch queue，同时将它们添加至一个组。

    dispatch_queue_t queue1 =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0);

    dispatch_group_t group1 =dispatch_group_create();

    NSArray *array = [NSArrayarray];

    for(id obj in array)

        dispatch_group_async(group1, queue1, ^{

            [selfdoSomethingIntensiveWith:obj];

        });

    dispatch_group_wait(group1,DISPATCH_TIME_FOREVER);

    dispatch_release(group1);