UITextField+TrailingPlaceholder.swift

import UIKit

extension UITextField {
    /// Add a trailing placeholder label that tracks the text as it changes
    func addTrailingPlaceholder(_ placeholder: String) {
        let label = UILabel()
        label.text = placeholder
        label.alpha = 0.3
        label.isHidden = true
        addSubview(label)
        addAction(UIAction { [weak self] _ in
            guard let self = self else {
                return
            }
            label.font = self.font
            label.frame = self.textRect(forBounds: self.bounds)
            label.frame.origin.x = (self.text ?? "").size(withAttributes: [
                .font: self.font as Any
            ]).width
            label.isHidden = !self.hasText
        }, for: .editingChanged)
    }
}