CODEWITHSUNDEEP
iosswiftanimationuiviewautolayout
GoldenJoe
GoldenJoe

Reputation: 8002

How can I define animations for views using auto layout without relying on tons of constraint references and boilerplate code?

Before the switch to auto layout, applying animations to a view was easy - you'd just change the frame in UIView.layoutWithDuration:. When constraints come into the picture, things get more complicated. The most common method of animating a view that uses auto layout is to keep a reference to the constraint(s) you want to change, then set the constant value, but this is very difficult to design around, and can affect other views if their constraints depend on the position of the view you want to animate.

There must be a better way to do this. I'd love to be able to do something like view.translateFrom(direction: .left, distance: 30, duration: 0.3, delay: 0).

Upvotes: 0

Views: 37

Answers (1)

Damo
Damo

Reputation: 12890

Ultimately you will want to use constraints to achieve simple animations. The overriding reason for this is -

"Choosing any other way is simply swimming against the stream"

If you don't want to 'litter' your classes with @IBOutlets for the constraints you wish to animate then you can in most cases obtain a reference to a pertinent constraint in code:

Handy extension

import UIKit

extension UIView {
  func constraint(attribute: NSLayoutAttribute) -> NSLayoutConstraint? {
    var constraint : NSLayoutConstraint? = .none

    for potentialCenterXConstraint in self.constraints {
      if potentialCenterXConstraint.firstAttribute == attribute {
        constraint = potentialCenterXConstraint
        break
      }
    }

    return constraint
  }
}

client code use

if let centerXConstraint = someView.constraint(attribute: .centerX) {

  // Do something funky with centerXConstraint
}

Upvotes: 1

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