IOS 8:dispatch Group adds

This is a comment section of a blog post, specially extracted, blog address: http://blog.cnbang.net/tech/2320/

The Dispatch group notifies you when the entire group's tasks are complete. These tasks can be synchronous or asynchronous, even in different queues. and Dispatch Group can notify you synchronously or asynchronously when the entire set of tasks is complete. Because the tasks to monitor are in different queues, use a dispatch_group_t instance to write down these different tasks.

Also, you need to notify batchofrequest when the entire set of tasks is complete.

IOS 8:dispatch Group adds