This search field animation is an example of "constraint animation". The constraint controls the size of an object. You can animation constraints to change height, width, and positions of your UI elements in iOS.

VIDEO TUTORIAL
https://youtu.be/_Sh8k70rSFk

PROJECT FILES
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How to Make Animations Bounce (Spring Animations) (iOS, Xcode 8, Swift 3)

Learn some really simple and cool animations that you can do today to give your users a better experience in your app!

Fun Animations with CGAffineTransform (Scale, Rotate, Reposition) Tutori...

In this video I will take you through and teach you how easy it is to do multiple animations using CGAffineTransform. I will even explain what "Affine" means. :D

How to Create Animation Chains - UIView.animate (iOS, Xcode 8, Swift 3)

Need to do multiple animations, one after another? This video will show you a pretty good way on how to accomplish this using UIView.animate with the completion block.

Simple Animations

UIView.animate(withDuration: 1) { 
    self.view.backgroundColor = UIColor.darkGray
}

And when you need a delay:

UIView.animate(withDuration: 4, delay: 5, options: [], animations: {
    self.view.backgroundColor = UIColor.darkGray
}, completion: nil)

What can be animated?

Here are some common properties (but not all):

• UIView.alpha - Use this to fade objects in or out. (Adjusts transparency)
• UIView.bounds - Defines the X,Y position of self (0,0) and the width, height of the object. Use to change the object's size or even position.
• UIView.center - Use to change the position of the object on the screen.
• UIView.frame - Defines the X,Y position inside its parent and the width, height of the object. Reposition or resize within a parent view.
• UIView.transform - Use this to rotate, scale, translate and skew objects.
• UIColor - Such as text color or background color. You can animate changing color such as in the example above.
• view.layoutIfNeeded() - Make changes to an object's constants and then call this function inside the animations block to see those changes animate.

(Swift 3)