init()
Creates a new group to which you can assign block objects.
Declaration
init()Return Value
The newly created group. In Objective-C returns NULL on failure.
Discussion
This function creates a new group with which block objects can be associated (by using the dispatch_group_async function). The dispatch group maintains a count of its outstanding associated tasks, incrementing the count when a new task is associated and decrementing it when a task completes. Functions such as dispatch_group_notify and dispatch_group_wait use that count to allow your application to determine when all tasks associated with the group have completed. At that time, your application can take any appropriate action.