Create a complete class-dump of Xcode, ready for adding to an empty Xcode project for all your header-ogling needs.

xcode-class-dump.sh

#!/bin/bash
# Creates a complete class-dump of Xcode and all its libs and internal plug-ins.
# Assumes you have Class-Dump in your path and Xcode at the location set via `xcode-select`.

xcodeClassDump=${1:-"$HOME/Documents/XcodeClassDump"}

xcodePath=`xcode-select -p`
sourceXcodeRootPath="$(dirname "$xcodePath")"

echo "Dumping from Xcode: $sourceXcodeRootPath"
echo "Creating dump in $xcodeClassDump"

# We need to `cd` into the directory, because we remove paths containing ".app" below and this would otherwise filter out everything contained in "Xcode.app".
cd "$sourceXcodeRootPath"

# Find all libraries and plug-ins within Xcode.app/Contents and call class-dump
# on each, preserving the folder structure in the output files.
# This will give many warnings like "doesn't contain an executable" or
# "Parsing method types failed". But it will succeed much more than it fails.
find . \( -iname "*.framework" -or -iname *.ideplugin \) ! -ipath *.platform* ! -ipath *.app* -print0 | xargs -0 -o -I % class-dump --arch x86_64 --sdk-mac -I -H -o "$xcodeClassDump/%" %

# Strip .framework and .ideplugin extensions from output folder names, so the
# files can be browsed more easily.
# (for example by adding the whole output folder to an empty Xcode project)
find "$xcodeClassDump" \( -iname "*.framework" -or -iname *.ideplugin \) -print | while read filename; do mv -v "$filename" "${filename%.*}"; done

If you have any comments or improvements, I'm looking forward to your input.