iOS Programming: The Big Nerd Ranch Guide

Timing Functions

The acceleration of the animation is controlled by its timing function. By default, animations use an ease-in/ease-out timing function. To use a driving analogy, this would mean the driver accelerates smoothly from rest to a constant speed and then gradually slows down at the end, coming to rest.

Other timing functions include linear (a constant speed from beginning to end), ease-in (accelerating to a constant speed and then ending abruptly), and ease-out (beginning at full speed and then slowing down at the end).

In ViewController.swift, update the animation in animateLabelTransitions() to use a linear timing function.

UIView.animateWithDuration(0.5,
    delay: 0,
    options: [.CurveLinear], animations: { self.currentQuestionLabel.alpha ...