Ruby's Object#define_method vs Module#define_method

Question

Can anyone elaborate on the differences between ruby's Object#define_method and Module#define_method and where they are generally used?

Answer 1

Object#define_method does not exist:

o = Object.new
o.define_method
#NoMethodError: undefined method `define_method' for #<Object:0x1448a80>

However, Object.define_method exists:

Object.define_method
#NoMethodError: private method `define_method' called for Object:Class

That's because Object is an object of class Class, and Class is a subclass of Module:

Object.class # => Class
Class.ancestors # => [Class, Module, Object, Kernel, BasicObject]

So when you call Object.define_method, you're calling Module#define_method.

Just remember that classes are objects of class Class, and it'll be as clear as mud!

Answer 2

Object#define_method is actually Module#define_method.

pry(main)> Object.method(:define_method).owner
=> Module
pry(main)> Module.method(:define_method).owner
=> Module