I m having trouble understanding the concept of eigenclass or singleton class in ruby. I read a lot that the eigenclass is a class's class. That doesn't make sense to me as for me a class's class i...

In Ruby, the method puts is a singleton method of the Kernel module. Normally, when a module is included or extended by another module, the module (but not its singleton class) is added to the inh...

I've been looking for a natural way to implement state-dependent behaviour (state machines) in Python objects. The goal was for objects to have a small number of states, or "mutually orthogonal" as...

Let's open class Module and add a method to it: class Module def foo puts "phew" end end I can call this method by doing this, Class.foo which is understandable because class of Class...

What does class << self do in Ruby?

Are class methods and methods in the eigenclass (or metaclass) of that class just two ways to define one thing? Otherwise, what are the differences? class X # class method def self.a "a" end...

This part works: class Example1 @@var1= "var1 in the Example1" def get_var1 @@var1 end end example1 = Example1.new example1.get_var1 # => "var1 in the Example1" but if I try eigencl...

In Ruby, getting the eigenclass of a class Foo is a simple as eigenclass = class << Foo; self; end #=> #<Class:Foo> eigenclass = Foo.singleton_class #2.1.0 #=> #<Class:Foo>...

I understand the regular method lookup path i.e. class, superclass/module, all the way up to BasicObject. I thought it was true for singleton version of the chain also but doesn't seem the case whe...

I have defined a module Vehicle like such module Vehicle class <<self def build end private def background end end end A call to Vehicle.singleton_methods returns [:build]. How c...

I was trying to limit the instantiation of a class to just a single one(without using singleton) but i couldn't. I tried with class variables (@@) but without luck. I googled it and came across thi...

Getting a list of all modules is easy in Ruby: ObjectSpace.each_object(Module).to_a However, is it possible to get a list of all eigenclasses (also known as singleton classes or metaclasses)? Or...

I am currently experimenting with Ruby and Rails, and I've hit a few sections in tutorials and books about metaprogramming. Many mention that it is an essential component of Ruby but they don't rea...

I've missed the memo somewhere, and I hope you'll explain this to me. Why is the eigenclass of an object different from self.class? class Foo def initialize(symbol) eigenclass = class << ...