LLDB Debugging: UI

I can never remember how to use LLDB when it comes time, and usually that’s in the most high pressure of moments. Jotting down a few notes on how to debug UI using LLDB. Some really powerful stuff here. See linked resource for more context and further details.

• Quickly get information on a view you’re looking at:
  1. po [[[UIApplication sharedApplication] keyWindow] recursiveDescription]
  2. Pick the memory address of the view from the hierarchy.
  3. po id $view = (id)0x123456f9
• To modify that view:
  1. po [$view setBackgroundColor:UIColor.redColor]
  2. Here’s the trick! Refresh the view with: [CATransaction flush]
• Couple random things I learned from reading this (and looking a few things up)
  • po , p, e are all aliases of expression (po runs command with the -O option, run help expression for details on what this does). Easy just to run po for everything.
  • With objective-c, I always had a hard time printing objects, but realized the issue is dot notation. Use brackets when running into property ‘someProperty’ not found on object of type ‘someObject’
  • This article adds (void) before sending a message to a selector (e.g. (void)[CATransaction flush]). It keeps from outputting anything, but doesn’t seem necessary.
  • Adding -- after expression is only required when you have options (to separate options from code you want to run).