Adding loading and reloading UI to everything owning a UIView

gistfile1.txt

````
import UIKit
import Foundation

public protocol LoadStateIndicating {
  /// Shows a blur view over the current context with an animated activity indicator.
  func startLoading()
  
  /// Hides blur view and activity indicator.
  func stopLoading()
  
  /// Shows reload option over blur view.
  func showReload(onReloadTarget: Any?, action: Selector)
  
  /// Hides reload option from blur view. Call `stopLoading()` to hide blur view altogether.
  func hideReload()
}

public protocol ContentPresenter: LoadStateIndicating {
  var mainView: UIView { get }
}

extension UIViewController: ContentPresenter {
  public var mainView: UIView {
    return self.view
  }
}

extension UITableViewController {
  public override var mainView: UIView {
    return self.view.subviews.first ?? self.view
  }
}

extension UICollectionViewController {
  public override var mainView: UIView {
    return self.view.subviews.first ?? self.view
  }
}

extension UIView: ContentPresenter {
  public var mainView: UIView {
    return self
  }
}

extension UITableViewCell {
  public override var mainView: UIView {
    return self.contentView
  }
}

extension UICollectionViewCell {
  public override var mainView: UIView {
    return self.contentView
  }
}

extension ContentPresenter {
  public func startLoading() {
    if let currentLoadingView = mainView.subviews.filter({ $0.tag == 101 }).first as? UIVisualEffectView, let activityView = currentLoadingView.contentView.subviews.first as? UIActivityIndicatorView {
      activityView.startAnimating()
      return
    }
    
    let activityView = UIActivityIndicatorView(activityIndicatorStyle: .white)
    activityView.color = UIColor(red: 27/255.0, green: 161/255.0, blue: 232/255.0, alpha: 1.0)
    activityView.hidesWhenStopped = true
    
    let blurView = UIVisualEffectView(effect: UIBlurEffect(style: .extraLight))
    blurView.tag = 101
    blurView.contentView.addSubview(activityView)
    mainView.addSubview(blurView)
    
    blurView.translatesAutoresizingMaskIntoConstraints = false
    blurView.widthAnchor.constraint(equalTo: mainView.widthAnchor).isActive = true
    blurView.heightAnchor.constraint(equalTo: mainView.heightAnchor).isActive = true
    blurView.centerXAnchor.constraint(equalTo: mainView.centerXAnchor).isActive = true
    blurView.centerYAnchor.constraint(equalTo: mainView.centerYAnchor).isActive = true
    
    activityView.translatesAutoresizingMaskIntoConstraints = false
    activityView.centerXAnchor.constraint(equalTo: blurView.contentView.centerXAnchor).isActive = true
    activityView.centerYAnchor.constraint(equalTo: blurView.contentView.centerYAnchor).isActive = true
    
    activityView.startAnimating()
  }
  
  public func stopLoading() {
    guard let blurView = mainView.subviews.filter({ $0.tag == 101 }).first as? UIVisualEffectView, let _ = blurView.contentView.subviews.first as? UIActivityIndicatorView else { return }
    
    blurView.removeFromSuperview()
  }
  
  public func hideReload() {
    guard let blurView = mainView.subviews.filter({ $0.tag == 101 }).first as? UIVisualEffectView, let _ = blurView.contentView.subviews.first as? UIActivityIndicatorView, let button = blurView.contentView.subviews[1] as? UIButton else { return }
    
    button.removeFromSuperview()
  }
  
  public func showReload(onReloadTarget target: Any?, action: Selector) {
    guard let blurView = mainView.subviews.filter({ $0.tag == 101 }).first as? UIVisualEffectView, let activityIndicator = blurView.contentView.subviews.first as? UIActivityIndicatorView else { return }
    
    activityIndicator.stopAnimating()
    
    let button = UIButton()
    button.setTitle("Retry", for: .normal)
    button.setTitleColor(.white, for: .normal)
    button.backgroundColor = UIColor(red: 27/255.0, green: 161/255.0, blue: 232/255.0, alpha: 1.0)
    button.layer.cornerRadius = 3.0
    
    button.addTarget(target, action: action, for: .touchUpInside)
    blurView.contentView.addSubview(button)
    
    button.translatesAutoresizingMaskIntoConstraints = false
    button.centerXAnchor.constraint(equalTo: blurView.contentView.centerXAnchor).isActive = true
    button.centerYAnchor.constraint(equalTo: blurView.contentView.centerYAnchor).isActive = true
  }
}

````