UIViewController+Embed.swift

extension UIViewController {
    
    func embed(_ child: UIViewController, animated: Bool = false) {
        let duration = animated ? 0.3 : 0.0
        
        child.view.alpha = 0
        child.willMove(toParent: self)
        self.addChild(child)
        self.view.addSubview(child.view)
        
        child.view.translatesAutoresizingMaskIntoConstraints = false
        self.view.topAnchor.constraint(equalTo: child.view.topAnchor).isActive = true
        self.view.bottomAnchor.constraint(equalTo: child.view.bottomAnchor).isActive = true
        self.view.leadingAnchor.constraint(equalTo: child.view.leadingAnchor).isActive = true
        self.view.trailingAnchor.constraint(equalTo: child.view.trailingAnchor).isActive = true
        self.view.setNeedsLayout()
        self.view.layoutIfNeeded()
        
        UIView.animate(withDuration: duration, animations: {
            child.view.alpha = 1
        }) { (completed) in
            child.didMove(toParent: self)
        }
    }
    
    func unembed(_ child: UIViewController, animated: Bool = false) {
        child.willMove(toParent: nil)
        let duration = animated ? 0.3 : 0.0
        
        UIView.animate(withDuration: duration, animations: {
            child.view.alpha = 0
        }) { (completed) in
            child.view.removeFromSuperview()
            child.removeFromParent()
            child.didMove(toParent: nil)
        }
    }
}