iOS 断点打印 view 层级

一、Printing the View Controller Hierarchy

_printHierarchy is a private method on UIViewController that you can use to print the view controller hierarchy to the console. Build and Run, select Push via storyboard and then hit the pause button in the Debug bar.
Now type this in the console and press return:

po [[[[UIApplication sharedApplication] keyWindow] rootViewController] _printHierarchy]

二、Printing the View Hierarchy

If you’re not a very visual person and prefer a textual overview of a view hierarchy, you can always use the age-old, and also private, recursiveDescription on UIView. This prints a view hierarchy very similar to the view controller hierarchy as demonstrated above.

JSQmessage.png

Build and Run, then select Push via Storyboard. The debugger should break as a JSQMessagesCollectionViewCellOutgoing is loaded. Now type the following into the console:

po [self.contentView recursiveDescription]

This will print the hierarchy of the JSQMessagesCollectionViewCellOutgoing’s contentView, which will look something like this:

<UIView: 0x7fde6c475de0; frame = (0 0; 312 170); gestureRecognizers = <NSArray: 0x7fde6c484fe0>; layer = <CALayer: 0x7fde6c474750>>
   | <JSQMessagesLabel: 0x7fde6c475eb0; baseClass = UILabel; frame = (0 0; 312 20); text = 'Today 10:58 PM'; clipsToBounds = YES; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fde6c476030>>
   | <JSQMessagesLabel: 0x7fde6c476400; baseClass = UILabel; frame = (0 20; 312 0); clipsToBounds = YES; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fde6c476580>>
   | <UIView: 0x7fde6c476b50; frame = (70 20; 210 150); autoresize = RM+BM; layer = <CALayer: 0x7fde6c474dd0>>
   |    | <UIImageView: 0x7fde6c482880; frame = (0 0; 210 150); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x7fde6c476ae0>> - (null)
   | <UIView: 0x7fde6c482da0; frame = (282 140; 30 30); autoresize = RM+BM; layer = <CALayer: 0x7fde6c482d00>>
   |    | <UIImageView: 0x7fde6c482e70; frame = (0 0; 30 30); opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x7fde6c482f70>> - (null)
   | <JSQMessagesLabel: 0x7fde6c483390; baseClass = UILabel; frame = (0 170; 312 0); clipsToBounds = YES; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fde6c483510>>

It’s rudimentary, but can be helpful when you want to debug a view hierarchy pre iOS 8.