Spinner2.swift

final class Spinner {

fileprivate static var activityIndicator: UIActivityIndicatorView?
fileprivate static var style: UIActivityIndicatorViewStyle = .whiteLarge
fileprivate static var baseBackColor = UIColor(white: 0, alpha: 0.6)
fileprivate static var baseColor = UIColor.white

/**
Add spinner to `UIView`

- Parameters:
    - view: The `UIView` being used to add the `UIActivityIndicatorView` onto
    - style: Style used for the `UIActivityIndicatorView`
    - backgroundColor: Display color
    - baseColor: Tint color of the spinner
*/
open static func start(from view: UIView,
                       style: UIActivityIndicatorViewStyle = Spinner.style,
                       backgroundColor: UIColor = Spinner.baseBackColor,
                       baseColor: UIColor = Spinner.baseColor) {

    guard Spinner.activityIndicator == nil else { return }

    let spinner = UIActivityIndicatorView(activityIndicatorStyle: style)
    spinner.backgroundColor = backgroundColor
    spinner.color = baseColor
    spinner.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(spinner)

    // Auto-layout constraints
    addConstraints(to: view, with: spinner)

    Spinner.activityIndicator = spinner
    Spinner.activityIndicator?.startAnimating()
}

/// Stops and removes `UIActivityIndicatorView`
open static func stop() {
    Spinner.activityIndicator?.stopAnimating()
    Spinner.activityIndicator?.removeFromSuperview()
    Spinner.activityIndicator = nil
}

/**
Add auto-layout constraints to provided `UIActivityIndicatorView`

- Parameters:
    - view: The view used to provide layout constraints
    - spinner: The `UIActivityIndicatorView` used to display
*/
fileprivate static func addConstraints(to view: UIView, with spinner: UIActivityIndicatorView) {
    spinner.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
    spinner.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    spinner.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
    spinner.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
}
}