iOS multi-threading Programming is always difficult for iOS development beginners to understand and master. Now through several examples, I will have a more systematic and comprehensive understanding of iOS multi-threading programming. I hope it will help Everyone helps.

Some programs are a straight line from the starting point to the end point; some programs are a circle that loops continuously until it is cut off. A straight line is like a simple Hello World. After running and printing, its life cycle is over, like a flash in the pan; a round one is like an operating system, which keeps running until you shut down.

A running program is a process or a task. A process contains at least one thread, and a thread is the execution flow of the program. When a program in Mac and iOS is started and a process is created, a thread starts running. This thread is called the main thread. The status of the main thread in the program is different from that of other threads. It is the final parent thread of other threads, and all interface display operations, that is, AppKit or UIKit operations, must be performed on the main thread. Friends in need can download and take a look