dispatch_Sources\dispatch_read\dispatch_I/O\dispatch_once\dispatch_set_target_queue 汇总

GCD Dispatch Sources

https://www.cnblogs.com/hlwfirst/p/5492493.html

GCD dispatch_read  与 dispatch_write  文件读写

http://blog.sina.com.cn/s/blog_6d01cce30101hzws.html

GCD Dispatch I/O

https://blog.csdn.net/u014205965/article/details/45922471

https://www.jianshu.com/p/da4710d76d33

GCD  dispatch_once

https://blog.csdn.net/yxys01/article/details/51579867

GCD  dispatch_set_target_queue 

https://blog.csdn.net/growinggiant/article/details/41077221