Runloop有效利用空閒時間

Runloop可被監聽的狀態

Runloop可被監聽的狀態是由CFRunLoopActivity結構體提供的：

public static var entry: CFRunLoopActivity { get }

    public static var beforeTimers: CFRunLoopActivity { get }

    public static var beforeSources: CFRunLoopActivity { get }

    public static var beforeWaiting: CFRunLoopActivity { get }

    public static var afterWaiting: CFRunLoopActivity { get }

    public static var exit: CFRunLoopActivity { get }

    public static var allActivities: CFRunLoopActivity { get }
複製代碼

利用Runloop空閒執行操做

let flags = CFRunLoopActivity.beforeWaiting
let runloopObserVer = CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault, flags.rawValue, true, 0) { (observer, activity) in
        self.perform(#selector(self.doSomething), with: nil, afterDelay: 0.01, inModes: [RunLoop.Mode.default])
    }
CFRunLoopAddObserver(CFRunLoopGetCurrent(), runloopObserVer, CFRunLoopMode.defaultMode)
複製代碼

這樣在beforeWaiting時會被監聽到而後執行操做。因爲執行操做又會喚醒Runloop這樣就會進入一個循環所以須要在適當的時候移除掉監聽：

CFRunLoopRemoveObserver(CFRunLoopGetCurrent(), runloopObserVer, CFRunLoopMode.defaultMode)
複製代碼