Multi-line UITextView with background and placeholder functionality of UITextField

TextField.swift

// This class is necessary to support "inset" (required to position placeholder appropriately
// in TextView)
//
class TextField: UITextField
{
    var inset: UIEdgeInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0);
    
    override func textRectForBounds(bounds: CGRect) -> CGRect
    {
        return UIEdgeInsetsInsetRect(bounds, inset);
    }
    
    override func placeholderRectForBounds(bounds: CGRect) -> CGRect
    {
        return UIEdgeInsetsInsetRect(bounds, inset);
    }
}

// This class implements a UITextView that has a UITextField behind it, where the UITextField
// provides the border and the placeholder text functionality (so that the TextView looks and 
// works like a UITextField in those respects).
//
class TextView : UITextView, UITextViewDelegate
{
    var textField = TextField();
    
    required init?(coder: NSCoder)
    {
        fatalError("This class doesn't support NSCoding.")
    }
    
    override init(frame: CGRect, textContainer: NSTextContainer?)
    {
        super.init(frame: frame, textContainer: textContainer);
        
        self.delegate = self;
        
        // Create a background TextField with clear (invisible) text and disabled
        self.textField.borderStyle = UITextBorderStyle.RoundedRect;
        self.textField.textColor = UIColor.clearColor();
        self.textField.userInteractionEnabled = false;

        // Align the background TextView to where text appears in the TextField, so that any
        // placeholder will be in the correct position.
        self.textField.contentVerticalAlignment = UIControlContentVerticalAlignment.Top;
        self.textField.inset = UIEdgeInsets(
            top: self.textContainerInset.top,
            left: self.textContainerInset.left + self.textContainer.lineFragmentPadding,
            bottom: self.textContainerInset.bottom,
            right: self.textContainerInset.right
        );
        
        // The background TextField should use the same font (for the placeholder)
        self.textField.font = self.font;
        
        self.addSubview(textField);
        self.sendSubviewToBack(textField);
    }
    
    convenience init()
    {
        self.init(frame: CGRectZero, textContainer: nil)
    }
    
    override var font: UIFont?
    {
        didSet
        {
            // Keep the font of the TextView and background textField in sync
            self.textField.font = self.font;
        }
    }
    
    var placeholder: String? = nil
    {
        didSet
        {
            self.textField.placeholder = self.placeholder;
        }
    }
    
    override func layoutSubviews()
    {
        super.layoutSubviews()
        // Do not scroll the background textView
        self.textField.frame = CGRectMake(0, self.contentOffset.y, self.frame.width, self.frame.height);
    }
    
    // UITextViewDelegate - Note: If you replace delegate, your delegate must call this
    func scrollViewDidScroll(scrollView: UIScrollView)
    {
        // Do not scroll the background textView
        self.textField.frame = CGRectMake(0, self.contentOffset.y, self.frame.width, self.frame.height);
    }
    
    // UITextViewDelegate - Note: If you replace delegate, your delegate must call this
    func textViewDidChange(textView: UITextView)
    {
        // Updating the text in the background textView will cause the placeholder to appear/disappear
        // (including any animations of that behavior - since the textView is doing this itself).
        self.textField.text = self.text;
    }
}