Swift extension to recreate a NSLayoutConstraint with a new multiplier and replace it

Example.swift

// In a UICollectionViewCell

@IBOutlet weak var leftStatConstraint: NSLayoutConstraint!

leftStatConstraint = leftStatConstraint.reapplyToView(self.contentView, multiplier: leftMultiplier)

NSLayoutConstraint+multiplier.swift

extension NSLayoutConstraint {
    /**
    Allows the copying of a layout constraint, just modifying the multiplier
    
    :param: multiplier the new multiplier to use
    
    :returns: the new layout constraint
    */
    public func copyWithMultiplier(multiplier: CGFloat) -> NSLayoutConstraint {
        let duplicate = NSLayoutConstraint(item: self.firstItem,
            attribute: self.firstAttribute,
            relatedBy: self.relation,
            toItem: self.secondItem,
            attribute: self.secondAttribute,
            multiplier: multiplier,
            constant: self.constant)
        duplicate.identifier = self.identifier
        
        return duplicate
    }
    
    /**
    Forms a new constraint with the specified multiplier. Disables the current one,
    applies the new one to the specified view and returns it.
    
    :param: view       the view to apply the new constraint to
    :param: multiplier the multiplier
    
    :returns: the newly formed constraint (disgard the original)
    */
    func reapplyToView(view: UIView, multiplier: CGFloat) -> NSLayoutConstraint {
        if multiplier == self.multiplier {
            return self
        }
        
        let newConstraint = self.copyWithMultiplier(multiplier)
        self.active = false
        view.addConstraint(newConstraint)
        
        return newConstraint
    }
}