Question

I’m very new to Ruby and now trying to understand something about metaprogramming.
I want to return missed method name:

class Numeric

  attr_accessor :method_name

  def method_missing(method_id)
    method_name = method_id.to_s
    self
  end

  def name
    method_name
  end

end

10.new_method.name #this should return new_method, but returns nil

Answer 1

Inside your method_missing, method_name is being interpreted as a local variable rather than the method_missing= mutator method that you’re expected. If you explicitly add the receiver then you’ll get what you want:

def method_missing(method_id)
  self.method_name = method_id.to_s
  self
end

Alternatively, you could assign to the @method_name instance variable:

def method_missing(method_id)
  @method_name = method_id.to_s
  self
end

The attr_accessor macro just adds two methods for you so attr_accessor :p is shorthand for this:

def p
    @p
end
def p=(v)
    @p = v
end

You’re free to use the underlying instance variable when you want or need to.