UIScreenEdgePanGestureRecognizer,螢幕邊緣滑動手勢作為一個比較冷門的手勢.其實用到的地方也沒想象中的那麼少.
UIScreenEdgePanGestureRecognizer是UIPanGestureRecognizer的子類.

點開UIScreenEdgePanGestureRecognizer的標頭檔案,發現這個類其實很輕巧的.

@property (readwrite, nonatomic, assign) UIRectEdge edges; //< The edges on which this gesture recognizes, relative to the current interface orientation
 

typedef NS_OPTIONS(NSUInteger, UIRectEdge) {
    UIRectEdgeNone   = 0,
    UIRectEdgeTop    = 1 << 0,
    UIRectEdgeLeft   = 1 << 1,
    UIRectEdgeBottom = 1 << 2,
    UIRectEdgeRight  = 1 << 3,
    UIRectEdgeAll    = UIRectEdgeTop | UIRectEdgeLeft | UIRectEdgeBottom | UIRectEdgeRight
} NS_ENUM_AVAILABLE_IOS(7_0);