Dynamically added instance method can not access class variable

user_1934428 0
Viewed 198

(Question already posted at Ruby Forum, but did not evoke any answer there).

This is my code:

class MC
  def initialize
    @x = 5
    @@y = 6
  end

  def f
    puts @x
    puts @@y
  end
end

m = MC.new
m.f

m.f produces the expected output without an error:

5
6

But this:

def m.g
  puts @x
  puts @@y
end

m.g

produces:

5
warning: class variable access from toplevel
NameError: uninitialized class variable @@y in Object

Why can I access @@y from f, but not from g?

Mentioning of toplevel and Object in the warning and the error message is puzzling to me.

@x is printed as 5, so its environment is MC. This excludes the possibility that @x and @@y in the definition of m.g refer to the toplevel environment (Object) instead of MC.

Why did I get the error message?

ruby
2 Answers
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