A UITextField subclass with the ability to show a loading spinner in its right view.

LoadingTextField.swift

import UIKit

class LoadingTextField: UITextField {

    // MARK: Public Properties

    var spinnerSpeed = 0.75
    var spinnerWidth: CGFloat = 3
    var spinnerDiameter: CGFloat = 18
    var isSpinnerRounded = true
    var offset: CGFloat = 16
    lazy var spinnerColor = textColor?.withAlphaComponent(0.6)
    
    var isLoading: Bool { _isLoading }
    
    // MARK: Private Properties
    
    private var _isLoading = false
    private let containerView = UIView()
    
    // MARK: Methods
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    
    private func commonInit() {
        // Draw a semi circle.
        containerView.frame = CGRect(x: 0, y: 0, width: spinnerDiameter, height: spinnerDiameter)
        let spinnerLayer = CAShapeLayer()
        let circlePath = UIBezierPath(arcCenter: CGPoint(x: containerView.frame.width / 2,
                                                         y: containerView.frame.width / 2),
                                      radius: containerView.frame.width / 2,
                                      startAngle: .zero, endAngle: .pi * 2, clockwise: true)
        spinnerLayer.path = circlePath.cgPath
        spinnerLayer.strokeColor = spinnerColor?.cgColor
        spinnerLayer.fillColor = nil
        spinnerLayer.lineWidth = spinnerWidth
        spinnerLayer.strokeStart = 0.5
        spinnerLayer.strokeEnd = 1
        spinnerLayer.lineCap = isSpinnerRounded ? .round : .butt
        containerView.layer.addSublayer(spinnerLayer)
        
        // Add it to the right view of the textfield.
        rightView = containerView
        rightViewMode = .always
        
        // Rotate the semi circle.
        let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
        rotateAnimation.fromValue = 0.0
        rotateAnimation.toValue = CGFloat(.pi * 2.0)
        rotateAnimation.duration = spinnerSpeed
        rotateAnimation.repeatCount = .greatestFiniteMagnitude
        containerView.layer.add(rotateAnimation, forKey: nil)
    }
    
    func startLoading() {
        if isLoading { return }
        _isLoading = true
        
        // Fade the loading spinner.
        containerView.alpha = 0
        UIView.animate(withDuration: 0.25, animations: {
            self.containerView.alpha = 1
        })
    }
    
    func stopLoading() {
        if !isLoading { return }
        _isLoading = false
        
        // Fade the loading spinner.
        UIView.animate(withDuration: 0.25, animations: {
            self.containerView.alpha = 0
        }, completion: { _ in
            self.containerView.removeFromSuperview()
        })
    }
}