Question

Can I create Ruby classes within functions bodies ?
I seem to be getting error which tells me its not allowed but I think it should be as classes are too objects here.

class A
    def method
        class B
        end
    end
end

This fails with error ‘class definition inside method body.
If we cant, why cant we create classes inside methods ?

Answer 1

class A
  def method
    self.class.const_set :B, Class.new {
      def foo
        'bar'
      end
    }
  end
end

A.new.method
A::B.new.foo # => 'bar'

However, why do you want to assign a constant inside a method? That doesn’t make sense: constants are constant, you can only assign to them once which means you can only run your method once. Then, why do you write a method at all, if it is only ever going to be run once, anyway?