Addition/subtraction of Ruby arrays

Let's say I have this array.

items = [
  {
    amount: 100,
    add: true
  },
  {
    amount: 50,
    add: false
  },
  {
    amount: 100,
    add: true
  }
]

What I want to do is add the amount if add is true and subtract it if add is false.

This code uses an extra total variable.

total = 0
items.each do |item|
  if item[:add]
    total += item[:amount]
  else
    total -= item[:amount]
  end
end

A one-liner code.

items.sum { |item| item[:add] ? item[:amount] : -item[:amount] }

I wonder if there is a better implementation for this problem. Is the one-liner readable enough?