In layman's language RunLoop (a): acquaintance

RunLoop series

In layman's language RunLoop (a): acquaintance
layman RunLoop (2): The data structures
in layman's language RunLoop (c): event loop mechanism
layman RunLoop (four): RunLoop thread
layman RunLoop (five): RunLoop and NSTimer
layman RunLoop (VI): Related interview questions

RunLoop Profile

• Operating cycle, the program is running loop to do something (e.g., receiving a message, processing the message, the sleep waiting, etc.);
• RunLoopThe object is to carry out a management of events / messages through the event loop internally maintained;
• RunLoopIs not a simple do...whileloop, it relates to the switching between the user mode and kernel mode.

Event Loop

Event loop is the event / message management, event loop can be achieved:

• When no messages to process, dormant thread to avoid resource consumption. Switch from user mode to kernel mode, waiting for a message;
• When there are messages to process immediately wake up the thread back to the user mode process messages;
• By calling the mach_msg()function to transfer control to the kernel state of the current thread / user mode.

The basic role of RunLoop

• To maintain continuous operation of the program:
  If you do not RunLoop, main()the function to perform a complete, the program will quit immediately.
  Our iOS program to keep the reason is that in continuous operation main()calls a function in UIApplicationMaina function, this function will start inside the main thread RunLoop;
• Handle various events (such as touch events, timer events, etc.) App of the;
• Saving CPU resources, improve program performance: When you do things that work, rest upon the rest.

RunLoop application areas

• Timer (Timer), PerformSelector
• GCD：dispatch_async(dispatch_get_main_queue(), ^{ });
• Incident response, gesture recognition interface refresh
• Network requests
• AutoreleasePool

RunLoop objects

• There are 2 sets of iOS API to access and use RunLoop:
  ① Foundation: NSRunLoop(a CFRunLoopRefpackage that provides object-oriented API)
  ② Core Foundation:CFRunLoopRef
• NSRunLoopAnd CFRunLoopRefthey represent the RunLoopobjects
• NSRunLoopNot open source, but CFRunLoopRefopen source: Core Foundation Source
• Gets RunLoopthe object of ways:

    // Foundation
    [NSRunLoop mainRunLoop];  // 获取主线程的 RunLoop 对象
    [NSRunLoop currentRunLoop];  // 获取当前线程的 RunLoop 对象
    // Core Foundation
    CFRunLoopGetMain();  // 获取主线程的 RunLoop 对象
    CFRunLoopGetCurrent();  // 获取当前线程的 RunLoop 对象

Application RunLoop in the actual development of

• Using port or custom input sources to communicate with other threads
• Use timers on child thread
• Solve the NSTimerproblem stops working when the slide
• Control thread life cycle, to achieve a permanent thread
• In any Cocoa application performSelector...method
• Monitoring applications Caton
• Performance Optimization
• …

Related Links

Core Foundation Source
Apple's official documentation RunLoop