Pixel Perfect Constraint

PixelPerfectConstraint.swift

import UIKit

/// A subclass of NSLayoutConstraint where the constant is in pixels and not points
final class PixelPerfectConstraint: NSLayoutConstraint {

    @IBInspectable var constantInPixels: Int = 0 {
        didSet {
            constant = CGFloat(constantInPixels) / UIScreen.mainScreen().scale
        }
    }
}