A simple drop in controller for making a UIView look busy

BusyController.swift

import UIKit

class BusyController<V: UIView> {
    
    let view: V
    
    var busyView: UIView? = nil
    var busyText: String = "Loading...".localized()
    
    init(view: V) {
        self.view = view
    }
    
    open var isBusy: Bool = false {
        didSet {
            if isBusy {
                addBusyView()
            } else {
                removeBusyView()
            }
        }
    }
    
    open var centerXAnchor: NSLayoutXAxisAnchor {
        return view.centerXAnchor
    }
    
    open var centerYAnchor: NSLayoutYAxisAnchor {
        return view.centerYAnchor
    }
    
    open func addBusyView() {
        if let _ = self.busyView {
            return
        }
        
        let busyView = UIView()
        busyView.translatesAutoresizingMaskIntoConstraints = false
        
        let activityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: .gray)
        activityIndicatorView.translatesAutoresizingMaskIntoConstraints = false
        activityIndicatorView.isHidden = false
        activityIndicatorView.startAnimating()
        busyView.addSubview(activityIndicatorView)
        
        let textLabel = UILabel()
        textLabel.translatesAutoresizingMaskIntoConstraints = false
        textLabel.text = busyText
        busyView.addSubview(textLabel)
        
        view.addSubview(busyView)
        
        NSLayoutConstraint.activate([
            NSLayoutConstraint(item: busyView, attribute: .leading, relatedBy: .equal, toItem: activityIndicatorView, attribute: .leading, multiplier: 1, constant: 0),
            NSLayoutConstraint(item: textLabel, attribute: .leading, relatedBy: .equal, toItem: activityIndicatorView, attribute: .trailing, multiplier: 1, constant: 5),
            NSLayoutConstraint(item: textLabel, attribute: .trailing, relatedBy: .equal, toItem: busyView, attribute: .trailing, multiplier: 1, constant: 0),
            NSLayoutConstraint(item: textLabel, attribute: .top, relatedBy: .equal, toItem: busyView, attribute: .top, multiplier: 1, constant: 0),
            NSLayoutConstraint(item: textLabel, attribute: .bottom, relatedBy: .equal, toItem: busyView, attribute: .bottom, multiplier: 1, constant: 0),
            NSLayoutConstraint(item: activityIndicatorView, attribute: .centerY, relatedBy: .equal, toItem: textLabel, attribute: .centerY, multiplier: 1, constant: 0)
        ])
        
        centerYAnchor.constraint(equalTo: busyView.centerYAnchor).isActive = true
        centerXAnchor.constraint(equalTo: busyView.centerXAnchor).isActive = true
        
        self.busyView = busyView
    }
    
    open func removeBusyView() {
        busyView?.removeFromSuperview()
        
        busyView = nil
    }
    
}

class BusyTableController: BusyController<UITableView> {
    
    override var centerXAnchor: NSLayoutXAxisAnchor {
        return view.frameLayoutGuide.centerXAnchor
    }
    
    override var centerYAnchor: NSLayoutYAxisAnchor {
        return view.frameLayoutGuide.centerYAnchor
    }
    
    override func addBusyView() {
        super.addBusyView()
        
        view.separatorStyle = .none
        view.setNeedsLayout()
    }
    
    override func removeBusyView() {
        super.removeBusyView()
        
        view.separatorStyle = .singleLine
        view.setNeedsLayout()
    }
    
}