Ruby -- ensuring local variable doesn't collide with method name

I'm trying to slim down my fat models by applying the Single Responsibility Principle. I'm culling out a lot of common code into mixins, which are then included into multiple classes. However, I'm running into this strange problem of local variables colliding with method names (or attr_accessors) of the class which includes the mixin. For example:

module MyAwesomeMixin
  def update_total
    my_total = self.pricing_items.reduce(0) {|sum, x| sum + x} # this borks if the "host class" has a method called my_total=
    total = my_total
  end
end

The code snippet above has complete unintended consequences if the "host class" has a method called my_total= How do I ensure that the my_total variable is completely inside the scope of update_total method and has absolutely nothing to do with the environment around it?

Solution

There's something you don't show us. In this case the only "unintented consequence" is that method my_total= is not called, because local var my_total is created.

module MyAwesomeMixin
  def update_total
    my_total = 10 # !> assigned but unused variable - my_total
  end
end

class Foo
  include MyAwesomeMixin

  attr_accessor :my_total
end

f = Foo.new
f.my_total # => nil
f.update_total
f.my_total # => nil

If you intend to call the setter, call it on self.

module MyAwesomeMixin
  def update_total
    self.my_total = 10
  end
end

f = Foo.new
f.my_total # => nil
f.update_total
f.my_total # => 10