(iOS) Load custom UIview in xib

AwakeAfter.swift

//Create the xib CustomView.xib and add the View class as CustomView (this one)

override func awakeAfter(using aDecoder: NSCoder) -> Any? {
        if self.subviews.isEmpty {
            let nib = UINib(nibName: "CustomView", bundle: nil)
            let viewArray = nib.instantiate(withOwner: nil, options: nil)
            guard let view = viewArray.first as? CustomView else {
                return self
            }
            view.translatesAutoresizingMaskIntoConstraints = false

            //Copy contsraints
            let heightAttr = NSLayoutConstraint.Attribute.height
            let heightConstraint = LayoutConstraintsHelper.findConstraint(onItem: self,
                                                                          attribute: heightAttr)

            let heightCon = heightConstraint.constant
            let newHeightConstraint =
                LayoutConstraintsHelper.heightConstraint(withValue: heightCon,
                                                         forViewA: view,
                                                         toViewB: nil)
            sizeConstraints.append(newHeightConstraint)

            let widthAttr = NSLayoutConstraint.Attribute.height
            let widthConstraint = LayoutConstraintsHelper.findConstraint(onItem: self,
                                                                         attribute: widthAttr)
            let widthCon = widthConstraint.constant
            let newWidthConstraint =
                LayoutConstraintsHelper.widthConstraint(withValue: widthCon,
                                                        forViewA: view,
                                                        toViewB: nil)
            sizeConstraints.append(newWidthConstraint)

            view.sizeConstraints = sizeConstraints
            return view
        }
        return self
    }

FileOwner.swift

//https://www.prolificinteractive.com/2017/06/09/xib-awakening-uniform-way-load-xibs/

/*
1. Create custom user-interface view file (name it CustomView)

2. Create a custom Swift file matching the name of the xib file

3. Set File Owner to be your custom class

4. Implement init methods, with a call to xibSetup()

5. Add a UIView in your UIViewController (located inside your Storyboard)

6. Set its class to CustomView

7. That’s it!
*/

extension UIView {
//1. Call this method from your init functions
  
  /// Helper method to init and setup the view from the Nib.
  func xibSetup() {
    let view = loadFromNib()
    addSubview(view)
    stretch(view: view)
  }
 
//2. Loads the view from the nib in the bundle
  
  /// Method to init the view from a Nib.
  ///
  /// - Returns: Optional UIView initialized from the Nib of the same class name.
  func loadFromNib<T: UIView>() -> T {
    let selfType = type(of: self)
    let bundle = Bundle(for: selfType)
    let nibName = String(describing: selfType)
    let nib = UINib(nibName: nibName, bundle: bundle)

    guard let view = nib.instantiate(withOwner: self, options: nil).first as? T else {
      fatalError(“Error loading nib with name \(nibName))”
    }

    return view
  }
 
//3. Resizes the loaded view, ready for use

  /// Stretches the input view to the UIView frame using Auto-layout
  ///
  /// - Parameter view: The view to stretch.
  func stretch(view: UIView) {
    view.translatesAutoresizingMaskIntoConstraints = false

    NSLayoutConstraint.active([
      view.topAnchor.constraint(equalTo: topAnchor),
      view.leftAnchor.constraint(equalTo: leftAnchor),
      view.rightAnchor.constraint(equalTo: rightAnchor),
      view.bottomAnchor.constraint(equalTo: bottomAnchor)
      ])
  }
}

@lamprosg How do I find the LayoutConstraintsHelper? Could you give me a keyword to find it?