How to print a control hierarchy in Cocoa?

Question

Carbon had a useful function called DebugPrintControlHierarchy.

Is there something similar for NSView or NSWindow?

Answer 1

I don't know what exactly DebugPrintControlHierarchy printed, but NSView has a useful method call _subtreeDescription which returns a string describing the entire hierarchy beneath the receiver, include classes, frames, and other useful information.

Don't be scared about the leading _ underscore. It's not public API, but it is sanctioned for public use in gdb. You can see it mentioned in the AppKit release notes along with some sample output.

Answer 2

Here's the guts of an NSView category I built awhile back:

+ (NSString *)hierarchicalDescriptionOfView:(NSView *)view 
                                      level:(NSUInteger)level
{

  // Ready the description string for this level
  NSMutableString * builtHierarchicalString = [NSMutableString string];

  // Build the tab string for the current level's indentation
  NSMutableString * tabString = [NSMutableString string];
  for (NSUInteger i = 0; i <= level; i++)
    [tabString appendString:@"\t"];

  // Get the view's title string if it has one
  NSString * titleString = ([view respondsToSelector:@selector(title)]) ? [NSString stringWithFormat:@"%@", [NSString stringWithFormat:@"\"%@\" ", [(NSButton *)view title]]] : @"";

  // Append our own description at this level
  [builtHierarchicalString appendFormat:@"\n%@<%@: %p> %@(%li subviews)", tabString, [view className], view, titleString, [[view subviews] count]];  

  // Recurse for each subview ...
  for (NSView * subview in [view subviews])
    [builtHierarchicalString appendString:[NSView hierarchicalDescriptionOfView:subview 
                                                                          level:(level + 1)]];

  return builtHierarchicalString;
}

- (void)logHierarchy
{
  NSLog(@"%@", [NSView hierarchicalDescriptionOfView:self
                                               level:0]);
}

Usage

Dump this into an NSView category, dump this in it. Include the category header wherever you want to use it, then call [myView logHierarchy]; and watch it go.

Answer 3

Swift 4.

macOS:

extension NSView {

   // Prints results of internal Apple API method `_subtreeDescription` to console.
   public func dump() {
      Swift.print(perform(Selector(("_subtreeDescription"))))
   }
}

iOS:

extension UIView {

   // Prints results of internal Apple API method `recursiveDescription` to console.
   public func dump() {
      Swift.print(perform(Selector(("recursiveDescription"))))
   }
}

Usage (in debugger): po myView.dump()