Fetch all the classes in the Object namespace...

class_detector.rb

def blacklist
  [
    :Object, :Module, :Class, :BasicObject, :Kernel, :NilClass, :NIL, :Data,
    :TrueClass, :TRUE, :FalseClass, :FALSE, :Encoding, :Comparable, :Method,
    :String, :Symbol, :Exception, :SystemExit, :SignalException, :Interrupt,
    :StandardError, :TypeError, :ArgumentError, :IndexError, :KeyError, :Dir,
    :RangeError, :ScriptError, :SyntaxError, :LoadError, :NotImplementedError,
    :NameError, :NoMethodError, :RuntimeError, :SecurityError, :NoMemoryError,
    :EncodingError, :SystemCallError, :Errno, :ZeroDivisionError, :Enumerable,
    :FloatDomainError, :Numeric, :Integer, :Fixnum, :Float, :Bignum, :Array,
    :Hash, :ENV, :Struct, :RegexpError, :Regexp, :MatchData, :Marshal, :Range,
    :IOError, :EOFError, :IO, :STDIN, :STDOUT, :STDERR, :ARGF, :FileTest, :File,
    :Time, :Random, :Signal, :Process, :Proc, :LocalJumpError, :UnboundMethod,
    :Binding, :Math, :GC, :ObjectSpace, :Enumerator, :StopIteration, :RubyVM,
    :Thread, :TOPLEVEL_BINDING, :ThreadGroup, :Mutex, :ThreadError, :Fiber,
    :FiberError, :Rational, :Complex, :RUBY_RELEASE_DATE, :RUBY_PLATFORM, :ARGV,
    :RUBY_PATCHLEVEL, :RUBY_REVISION, :RUBY_DESCRIPTION, :RUBY_COPYRIGHT, :Gem,
    :RUBY_ENGINE, :TracePoint, :RbConfig, :Config, :CROSS_COMPILING, :Date, :IRB,
    :Exception2MessageMapper, :RubyToken, :RubyLex, :Readline, :SystemStackError
  ] + ENV.keys.map(&:to_sym)
end

def constants_for name
  (name.constants - blacklist).map { |constant| name.const_get constant }
end

def classes_for constant
  if constant.is_a? Class
    [constant]
  elsif constant.is_a? Module
    constants_for(constant).inject([]) do |array,constant|
      array << classes_for(constant)
      array
    end
  else
    []
  end
end

def constants
  constants_for(Object)
end
def classes
  constants.map { |const| classes_for const }.flatten
end

module A
  class B
  end
end
class C
end

puts "Consts  => #{constants}"
puts "Classes => #{classes}"

Seems that one of my classes are causing an issue here, but this is more than enough to get me going anyway - thanks! :)

irb(main):001:0> def blacklist
irb(main):002:1>   [
irb(main):003:2*     :Object, :Module, :Class, :BasicObject, :Kernel, :NilClass, :NIL, :Data,
irb(main):004:2*     :TrueClass, :TRUE, :FalseClass, :FALSE, :Encoding, :Comparable, :Method,
irb(main):005:2*     :String, :Symbol, :Exception, :SystemExit, :SignalException, :Interrupt,
irb(main):006:2*     :StandardError, :TypeError, :ArgumentError, :IndexError, :KeyError, :Dir,
irb(main):007:2*     :RangeError, :ScriptError, :SyntaxError, :LoadError, :NotImplementedError,
irb(main):008:2*     :NameError, :NoMethodError, :RuntimeError, :SecurityError, :NoMemoryError,
irb(main):009:2*     :EncodingError, :SystemCallError, :Errno, :ZeroDivisionError, :Enumerable,
irb(main):010:2*     :FloatDomainError, :Numeric, :Integer, :Fixnum, :Float, :Bignum, :Array,
irb(main):011:2*     :Hash, :ENV, :Struct, :RegexpError, :Regexp, :MatchData, :Marshal, :Range,
irb(main):012:2*     :IOError, :EOFError, :IO, :STDIN, :STDOUT, :STDERR, :ARGF, :FileTest, :File,
irb(main):013:2*     :Time, :Random, :Signal, :Process, :Proc, :LocalJumpError, :UnboundMethod,
irb(main):014:2*     :Binding, :Math, :GC, :ObjectSpace, :Enumerator, :StopIteration, :RubyVM,
irb(main):015:2*     :Thread, :TOPLEVEL_BINDING, :ThreadGroup, :Mutex, :ThreadError, :Fiber,
irb(main):016:2*     :FiberError, :Rational, :Complex, :RUBY_RELEASE_DATE, :RUBY_PLATFORM, :ARGV,
irb(main):017:2*     :RUBY_PATCHLEVEL, :RUBY_REVISION, :RUBY_DESCRIPTION, :RUBY_COPYRIGHT, :Gem,
irb(main):018:2*     :RUBY_ENGINE, :TracePoint, :RbConfig, :Config, :CROSS_COMPILING, :Date, :IRB,
irb(main):019:2*     :Exception2MessageMapper, :RubyToken, :RubyLex, :Readline, :SystemStackError
irb(main):020:2>   ] + ENV.keys.map(&:to_sym)
irb(main):021:1> end
=> nil

irb(main):022:0>  
irb(main):023:0* def constants_for name
irb(main):024:1>   (name.constants - blacklist).map { |constant| name.const_get constant }
irb(main):025:1> end
=> nil

irb(main):026:0>  
irb(main):027:0* def classes_for constant
irb(main):028:1>   if constant.is_a? Class
irb(main):029:2>     [constant]
irb(main):030:2>   elsif constant.is_a? Module
irb(main):031:2>     constants_for(constant).inject([]) do |array,constant|
irb(main):032:3*       array << classes_for(constant)
irb(main):033:3>       array
irb(main):034:3>     end
irb(main):035:2>   else
irb(main):036:2*     []
irb(main):037:2>   end
irb(main):038:1> end
=> nil

irb(main):039:0>  
irb(main):040:0* def constants
irb(main):041:1>   constants_for(Object)
irb(main):042:1> end
=> nil

irb(main):043:0> def classes
irb(main):044:1>   constants.map { |const| classes_for const }.flatten
irb(main):045:1> end
=> nil

irb(main):046:0>  
irb(main):047:0* module A
irb(main):048:1>   class B
irb(main):049:2>   end
irb(main):050:1> end
=> nil
irb(main):051:0> class C
irb(main):052:1> end
=> nil
irb(main):053:0>  
irb(main):054:0* puts "Consts  => #{constants}"
Consts  => ["1.9.2", "/home/leafpile/app/current", ConditionVariable, Queue, SizedQueue, Etc, Syck, Psych, StringIO, DateTime, Syck, Yajl, JSON, Faker, OpenStruct, Shellwords, URI, Rack, ERB, StringScanner, StringScanner::Error, FileUtils, Set, SortedSet, Delegator, SimpleDelegator, Tempfile, Sinatra, Digest, Tilt, Monk, OpenSSL, Fcntl, SecureRandom, MonitorMixin, Monitor, Logger, Base64, BasicSocket, Socket, SocketError, IPSocket, TCPSocket, TCPServer, UDPSocket, UNIXSocket, UNIXServer, Addrinfo, Redis, Timeout, Timeout::Error, Ohm, Haml, CGI, Rtopia, I18n, Pagination, CanCan, Nest, Ost, RSolr, LightConfig, Sunspot, IPAddr, Mail, ActiveSupport, ActiveSupport::HashWithIndifferentAccess, Net, MIME, Singleton, Treetop, IntervalSkipList, Forwardable, SingleForwardable, CSV, Iconv, Spreadsheet, RecursivelyEnumerable, Ole, RangesIO, RangesIONonResizeable, Translatable, CanonicalizeGender, JsFiles, AuditTrail, PhoneNumber, AddressParser, Mac, UUIDGen, UUID, OpenURI, GoogleSearch, SolrIndexing, DuplicationMarking, LazyAssignTagIds, Paranoia, Taggability, TagInheritance, PersonContactDetailsConcerns, PersonSunspotConcerns, HasContactDetails, HasDocuments, GroupByHelpers, HasCommunications, List, BigDecimal, Person, CanonicalizeMaritalStatus, Nokogiri, Racc, Racc::ParseError, ImageGrabber, HasCandidates, CountryCode, FixActions, Assignments, AssignmentSunspotConcerns, Assignment, CanonicalizeAssignmentStatus, EncodingHelpers, BizDevs, BizDevSunspotConcerns, BizDev, CanonicalizeBizDevCandidateStage, OhmInstanceAdapter, OhmDataAccessor, UserAgent, CompanySunspotConcerns, Company, CanonicalizeCompanyStatus, Readability, HasActivityTypes, PdfToText, CanonicalizeBizDevStatus, CanonicalizeCountry, LP, Sequel, LegacyConnect, Repeater, OpenOffice, Main, Benchmark, ContactDetailsHelpers, TagHelpers, CountriesHelpers, IconHelpers, UserAgentHelpers, IfHelpers, IPHelpers, AddressHelpers, Mobile, Biography, TagNote, Education, PersonSearch, ContactDetailPresenter, BizDevCandidateSunspotConcerns, BizDevCandidate, Candidates, CandidateSunspotConcerns, Candidate, Address, Ability, Document, SourceSunspotConcerns, Source, AdvancedSearchQuery, Job, CandidateActivity, UserSunspotConcerns, User, ContactDetail, ContactLogSunspotConcerns, Communication, DuplicationNotice, Notification, Indexer, CompanyInfo, BizDevCandidateActivity, School, SubContactLog, SheetExporter, MergedPerson, Connection, TagSunspotConcerns, Tags, Email, Synonym, MergedCompany, AccessLog, IPRange, MergedPosition, Group, Tag, PositionSunspotConcerns, Comment, Duplicate, Position, DesignTest, A, C]

=> nil

irb(main):055:0> puts "Classes => #{classes}"
LoadError: no such file to load -- fcgi
  from /home/leafpile/app/current/vendor/rack-1.3.0/lib/rack/handler/fastcgi.rb:1:in `require'
  from /home/leafpile/app/current/vendor/rack-1.3.0/lib/rack/handler/fastcgi.rb:1:in `<top (required)>'
  from (irb):24:in `const_get'
  from (irb):24:in `block in constants_for'
  from (irb):24:in `map'
  from (irb):24:in `constants_for'
  from (irb):31:in `classes_for'
  from (irb):32:in `block in classes_for'
  from (irb):31:in `each'
  from (irb):31:in `inject'
  from (irb):31:in `classes_for'
  from (irb):44:in `block in classes'
  from (irb):44:in `map'
  from (irb):44:in `classes'
  from (irb):55
  from /usr/bin/irb:12:in `<main>'
irb(main):056:0> 

It also might be because I setup the blacklist based on 2.0.0 constants, just add the extra 1.9.2 ones into the black list...