What is an elegant way of modifying last element of an array?

Question

I have an array of custom class objects and I need to modify a property of the last element. I know "last" and "first" are implemented as getters, however, that doesn't help me :) Is there another way than accessing the last element by index?

UPDATE

protocol DogProtocol {

  var age: Int {get set}
}

class Dog: DogProtocol {
  var age = 0
}

var dogs = Array<DogProtocol>()
dogs.append(Dog())
dogs.last?.age += 1 // Generates error in playground: left side of mutating operator isn't mutable: 'last" is a get-only property

Answer 1

Safe (in case of empty) and elegant:

foo.indices.last.map{ foo[$0].bar = newValue }

Mind you only do this with Sequencess (like Array) as with collections getting the last index may require iterating the whole thing.