Dispatch_sync: synchronous, without the ability to open threads Dispatch_async: Asynchronous, with the ability to open threads

Dispatch_sync: synchronous, without the ability to open threads

Dispatch_async: Asynchronous, with the ability to open threads

Concurrent queues: Multiple tasks can be executed concurrently

Walkthrough Queue: Once a task has finished executing, the next task is executed.

Data conversion between the core Foundation and foundation framework requires bridging _bridge NSString cfstring

Navigation controller push enters the next controller

Xib do not put more than one object, you may return to the object [object Superview]; There may be an error xib is generally used to place on the view of the controller as part of it, not as the entire view of the controller.

Xib is the name of the view Xib not the same as the controller name and not the same name as the controller after it is removed.

The controller will default to find the corresponding xib to create view,1, look for the controller to remove the name of the controllers Word Xib 2, the exact same name Xib

Dispatch_sync: synchronous, without the ability to open threads Dispatch_async: Asynchronous, with the ability to open threads