XCode debugger data formatters

Apple XCode has a (still) hidden plugin structure to visualize your own data structures inside the debugger view.
It is possible to change the summary by editing a plist file or make your own plugin to visualize more complex data.

The debugger viewer for LibXML2

The sources are available via the sourceforge CVS system.
A binary for XCode 3 and 2 is available via the files download of the project.
With XCode 3, the installation locations changed. Copying the bundle file to $HOME/Library/Application Support/Developer/Shared/Xcode/CustomDataViews. More information on the location is found at Stack Overvlow on the xcode data formatter bundle
For XCode 2, installation is copying the bundle file to $HOME/Library/Application Support/Apple/Developer Tools/CustomDataViews. The $HOME is your home directory (/Users/name).

Create your own customizations

You have the option (or it is already available) to put at that same spot a CustomDataViews.plist containing rules to format data. The format is described on a seperate page.

Create your own XCode debugger plugin

In order to create your own, it is the easiest to check out the source code of this plugin and use that as a basis for your own. The explanation is described on a seperate page.