UIView *view = [[UIView alloc] init];
NSLog(@"%@", [view performSelector:@selector(_ivarDescription)]);
<UIView: 0x7fa18a7022d0>:
in UIView:
_constraintsExceptingSubviewAutoresizingConstraints (NSMutableArray*): nil
_cachedTraitCollection (UITraitCollection*): nil
_layer (CALayer*): <CALayer: 0x604000222ac0>
_layerRetained (CALayer*): <CALayer: 0x604000222ac0>
_enabledGestures (int): 0
_gestureRecognizers (NSMutableArray*): nil
_window (UIWindow*): nil
_subviewCache (NSArray*): nil
_templateLayoutView (UIView*): nil
_charge (float): 0
_tag (long): 0
_viewDelegate (UIViewController*): nil
_backgroundColorSystemColorName (NSString*): nil
_countOfMotionEffectsInSubtree (unsigned long): 0
_unsatisfiableConstraintsLoggingSuspensionCount (unsigned long): 0
_countOfTraitChangeRespondersInDirectSubtree (unsigned long): 1
_cachedScreenScale (double): 0
_viewFlags (struct ?): {
userInteractionDisabled (b1): NO
implementsDrawRect (b1): NO
implementsDidScroll (b1): NO
implementsMouseTracking (b1): NO
implementsIntrinsicContentSize (b1): NO
hasBackgroundColor (b1): NO
......