How to find out all classes of ruby corelib? - ruby

Question

I need to return an Array of all classes that are part of ruby core.
http://ruby-doc.org/core-2.2.3/
For instance, the array should be like this:
[Array, String, Hash etc..]
Can also be strings instead such as:
['Array', 'String', 'Hash']
This should lateron be used for looking up documentation of ri, but prior to invoke ri - and it must only work for ruby core docu, deliberately not so for any other part of ruby (vanilla ruby is to be targeted for one project here, and the only constant to be usable is the default ruby install on the user's computer).
Thanks.

Answer 1

ObjectSpace.each_object(Class). # Get all instances of `Class`
reject {|klass| klass.name.nil? } # Reject singleton classes
# => [ARGF.class, ArgumentError, Array, BasicObject, Bignum, Binding, Class,
# Complex, Complex::compatible, Data, Dir, EOFError, Encoding,
# Encoding::CompatibilityError, Encoding::Converter,
# Encoding::ConverterNotFoundError, Encoding::InvalidByteSequenceError,
# Encoding::UndefinedConversionError, EncodingError, Enumerator,
# Enumerator::Generator, Enumerator::Lazy, Enumerator::Yielder, Errno::E2BIG,
# Errno::EACCES, Errno::EADDRINUSE, Errno::EADDRNOTAVAIL, Errno::EAFNOSUPPORT,
# Errno::EAGAIN, Errno::EALREADY, Errno::EAUTH, Errno::EBADF, Errno::EBADMSG,
# Errno::EBADRPC, Errno::EBUSY, Errno::ECANCELED, Errno::ECHILD,
# Errno::ECONNABORTED, Errno::ECONNREFUSED, Errno::ECONNRESET, Errno::EDEADLK,
# Errno::EDESTADDRREQ, Errno::EDOM, Errno::EDQUOT, Errno::EEXIST,
# Errno::EFAULT, Errno::EFBIG, Errno::EFTYPE, Errno::EHOSTDOWN,
# Errno::EHOSTUNREACH, Errno::EIDRM, Errno::EILSEQ, Errno::EINPROGRESS,
# Errno::EINTR, Errno::EINVAL, Errno::EIO, Errno::EISCONN, Errno::EISDIR,
# Errno::ELOOP, Errno::EMFILE, Errno::EMLINK, Errno::EMSGSIZE,
# Errno::EMULTIHOP, Errno::ENAMETOOLONG, Errno::ENEEDAUTH, Errno::ENETDOWN,
# Errno::ENETRESET, Errno::ENETUNREACH, Errno::ENFILE, Errno::ENOATTR,
# Errno::ENOBUFS, Errno::ENODATA, Errno::ENODEV, Errno::ENOENT,
# Errno::ENOEXEC, Errno::ENOLCK, Errno::ENOLINK, Errno::ENOMEM, Errno::ENOMSG,
# Errno::ENOPROTOOPT, Errno::ENOSPC, Errno::ENOSR, Errno::ENOSTR,
# Errno::ENOSYS, Errno::ENOTBLK, Errno::ENOTCONN, Errno::ENOTDIR,
# Errno::ENOTEMPTY, Errno::ENOTRECOVERABLE, Errno::ENOTSOCK, Errno::ENOTSUP,
# Errno::ENOTTY, Errno::ENXIO, Errno::EOPNOTSUPP, Errno::EOVERFLOW,
# Errno::EOWNERDEAD, Errno::EPERM, Errno::EPFNOSUPPORT, Errno::EPIPE,
# Errno::EPROCLIM, Errno::EPROCUNAVAIL, Errno::EPROGMISMATCH,
# Errno::EPROGUNAVAIL, Errno::EPROTO, Errno::EPROTONOSUPPORT,
# Errno::EPROTOTYPE, Errno::ERANGE, Errno::EREMOTE, Errno::EROFS,
# Errno::ERPCMISMATCH, Errno::ESHUTDOWN, Errno::ESOCKTNOSUPPORT,
# Errno::ESPIPE, Errno::ESRCH, Errno::ESTALE, Errno::ETIME, Errno::ETIMEDOUT,
# Errno::ETOOMANYREFS, Errno::ETXTBSY, Errno::EUSERS, Errno::EXDEV,
# Errno::NOERROR, Exception, FalseClass, Fiber, FiberError, File, File::Stat,
# Fixnum, Float, FloatDomainError, Gem::BasicSpecification,
# Gem::CommandLineError, Gem::ConflictError, Gem::DependencyError,
# Gem::DependencyRemovalException, Gem::DependencyResolutionError,
# Gem::DocumentError, Gem::EndOfYAMLException, Gem::ErrorReason,
# Gem::Exception, Gem::FilePermissionError, Gem::FormatException,
# Gem::GemNotFoundException, Gem::GemNotInHomeException,
# Gem::ImpossibleDependenciesError, Gem::InstallError,
# Gem::InvalidSpecificationException, Gem::List, Gem::LoadError,
# Gem::OperationNotSupportedError, Gem::Platform, Gem::PlatformMismatch,
# Gem::RemoteError, Gem::RemoteInstallationCancelled,
# Gem::RemoteInstallationSkipped, Gem::RemoteSourceException, Gem::Requirement,
# Gem::Requirement::BadRequirementError, Gem::RubyVersionMismatch,
# Gem::SourceFetchProblem, Gem::SpecificGemNotFoundException,
# Gem::Specification, Gem::StubSpecification, Gem::StubSpecification::StubLine,
# Gem::SystemExitException, Gem::UnsatisfiableDependencyError,
# Gem::VerificationError, Gem::Version, Hash, IO, IO::EAGAINWaitReadable,
# IO::EAGAINWaitWritable, IO::EINPROGRESSWaitReadable,
# IO::EINPROGRESSWaitWritable, IOError, IndexError, Integer, Interrupt,
# KeyError, LoadError, LocalJumpError, MatchData, Math::DomainError, Method,
# Module, Monitor, MonitorMixin::ConditionVariable,
# MonitorMixin::ConditionVariable::Timeout, Mutex, NameError,
# NameError::message, NilClass, NoMemoryError, NoMethodError,
# NotImplementedError, Numeric, Object, ObjectSpace::WeakMap, Proc,
# Process::Status, Process::Tms, Process::Waiter, Random, Range, RangeError,
# Rational, Rational::compatible, Regexp, RegexpError, RubyVM, RubyVM::Env,
# RubyVM::InstructionSequence, RuntimeError, ScriptError, SecurityError,
# SignalException, StandardError, StopIteration, String, StringIO, Struct,
# Symbol, SyntaxError, SystemCallError, SystemExit, SystemStackError, Thread,
# Thread::Backtrace, Thread::Backtrace::Location, Thread::ConditionVariable,
# Thread::Queue, Thread::SizedQueue, ThreadError, ThreadGroup, Time,
# TracePoint, TrueClass, TypeError, UnboundMethod, UncaughtThrowError,
# ZeroDivisionError, fatal]
Note, however, that by artificially restricting yourself to classes, you miss out on some rather important methods which are defined in modules, for example Kernel#puts and Kernel#require.
I removed singleton classes from the list, because it would have become just too cluttered, but unfortunately, this means that you are now missing, for example, using, which is defined in the singleton class of the anonymous top-level object usually called main.
You also miss out on pre-defined values that are not classes or modules, such as Float::INFINITY, true, false, nil, etc.
Note also that this will return all classes loaded, not only those from the core library, but also implementation-specific classes. The whole RubyVM namespace, for example, is a private internal implementation detail of YARV and doesn't exist on other Ruby implementations. Likewise, Fixnum and Bignum are not guaranteed to exist, the Ruby Language Specification only guarantees that there is an Integer class which may or may not have zero or more implementation-specific subclasses.
A better approach to guaranteeing that your code runs on all Ruby implementations would be to restrict yourself to the language, modules and classes defined in the ISO Ruby Language Specification.