Interpolate

Interpolate is a powerful Swift interpolation framework for creating interactive gesture-driven animations.

Usage

The 🔑 idea of Interpolate is - all animation is the interpolation of values over time.

To use Interpolate:

Import Interpolate at the top of your Swift file.

import Interpolate

Create an Interpolate object with a from value, a to value and an apply closure that applies the interpolation's result to the target object.

let colorChange = Interpolate(from: UIColor.whiteColor(),
to: UIColor.redColor(),
apply: { [weak self] (result) in
    if let color = result as? UIColor {
      self?.view.backgroundColor = color
    }
})

Next, you will need to define a way to translate your chosen gesture's progress to a percentage value (i.e. a CGFloat between 0.0 and 1.0).

For a gesture recognizer or delegate that reports every step of its progress (e.g. UIPanGestureRecognizer or a ScrollViewDidScroll) you can just apply the percentage directly to the Interpolate object:

@IBAction func handlePan(recognizer: UIPanGestureRecognizer) {
    let translation = recognizer.translationInView(self.view)
    let translatedCenterY = view.center.y + translation.y
    let progress = translatedCenterY / self.view.bounds.size.height
    colorChange.progress = progress
}

For other types of gesture recognizers that only report a beginning and an end (e.g. a UILongPressGestureRecognizer), you can animate directly to a target progress value with a given duration. For example:

@IBAction func handleLongPress(recognizer: UILongPressGestureRecognizer) {
    switch recognizer.state {
        case .Began:
            colorChange.animate(1.0, duration: 0.3)
        case .Cancelled, .Ended, .Failed:
            colorChange.animate(0.0, duration: 0.3)
        default: break
    }
}

To stop an animation:

colorChange.stopAnimation()

When you are done with the interpolation altogether:

colorChange.invalidate()

Voila!

What can I interpolate?

Interpolate currently supports the interpolation of:

• CGPoint
• CGRect
• CGSize
• Double
• CGFloat
• Int
• NSNumber
• UIColor
• CGAffineTransform
• CATransform3D

More types will be added over time.

Advanced usage

Interpolate is not just for dull linear interpolations.

For smoother animations, consider using any of the following functions: EaseIn, EaseOut, EaseInOut and Spring.

// Spring interpolation
let shadowPosition = Interpolate(from: -shadowView.frame.size.width,
to: (self.view.bounds.size.width - shadowView.frame.size.width)/2,
function: SpringInterpolation(damping: 30.0, velocity: 0.0, mass: 1.0, stiffness: 100.0),
apply: { [weak self] (result) in
  if let originX = result as? CGFloat {
      self?.shadowView.frame.origin.x = originX
  }
})

// Ease out interpolation
let groundPosition = Interpolate(from: CGPointMake(0, self.view.bounds.size.height),
to: CGPointMake(0, self.view.bounds.size.height - 150),
function: BasicInterpolation.EaseOut,
apply: { [weak self] (result) in
    if let origin = result as? CGPoint {
        self?.groundView.frame.origin = origin
    }
})

In fact, you can easily create and use your own interpolation function - all you need is an object that conforms to the InterpolationFunction protocol.

Setting up with CocoaPods

source 'https://github.com/CocoaPods/Specs.git'
pod 'Interpolate', '~> 0.1'

Setting up with Carthage

Carthage is a decentralized dependency manager that automates the process of adding frameworks to your Cocoa application.

You can install Carthage with Homebrew using the following command:

$ brew update
$ brew install carthage

To integrate Interpolate into your Xcode project using Carthage, specify it in your Cartfile:

github "marmelroy/Interpolate"

Inspiration

• https://github.com/icanzilb/EasyAnimation
• https://github.com/robb/RBBAnimation
• https://github.com/facebook/pop
• http://bojackhorseman.com