In Ruby how do I call a base class method from a different method in a derived class that overrides that same method?

If I have a base class with method 'a' and a derived class that reimplements method 'a', I can call Base.a from Derived.a by just calling super; how do I call the base class 'a' from a different derived class method?

class Base
  def a
    puts "hi, this is Base.a"
  end

end

class Derived < Base
  def a
    puts "hi, this is Derived.a"
  end

  def b
    # here is where I want to call Base.a
    Base.a  # this doesn't work
    
  end
end

You can use the method Method#super_method:

class Base
  def a
    puts "hi, this is Base.a"
  end
end

<!-->
class Derived < Base
def a
puts "hi, this is Derived.a"
end

  def b
    # here is where I want to call Base.a
    method(:a).super_method.call
  end
end

<!-->
Derived.new.b
hi, this is Base.a

More generally, you could have arguments and/or a block.

class Base
  def c(x, &block)
    puts "ho, this is Base.c"
    block.call(3*x)
  end  
end

<!-->
class Derived < Base
def c(x, &block)
puts "ho, this is Derived.c"
block.call(x)
end

  def d(x, &block)
    method(:c).super_method.call(x, &block)
  end
end

<!-->
Derived.new.d(5) { |x| puts "#{x} is a lot" }
ho, this is Base.c
15 is a lot

You could also do the following.

class A
  def a
    "A.a"
  end
end

<!-->
class B < A
def a
"B.a"
end
end
<!-->
class C<B
def a
"C.a"
end
<!-->
def test
method(:a).super_method.super_method.call
end
end
<!-->
C.new.test
#=> "A.a"

alias_method can do it:
> Makes new_name a new copy of the method old_name. This can be used to retain access to methods that are overridden.

https://rubyapi.org/3.2/o/module#method-i-alias_method

class Base
  def a
    puts "hi, this is Base.a"
  end
end

class Derived < Base
  alias_method :base_a, :a

  def a
    puts "hi, this is Derived.a"
  end

  def b
    base_a
  end
end

>> Derived.new.b
hi, this is Base.a
>> Derived.new.a
hi, this is Derived.a