LH17

enum StatesType: String {
    case error = "error"
    case empty = "empty"
    case loading = "loading"
    case none = "none"
}

LH17

extension ViewStateProtocol where Self: UIViewController {
    ..........
     // Manages and adds different views on the basis of the state
    func addView(withState state: StatesType) {
        
        // error state, empty state & loading state
        switch state {
        case .loading:
            // calls state manager to add a laoding view
            stateManager?.addView(loadingView!, forState: StatesType.loading.rawValue, superview: view)

LH17

extension ViewStateProtocol where Self: UIViewController {
    
    // State manager class to remove/add views
    var stateManager: StateManager? {
        return StateManager.sharedInstance
    }
    
    // Loading view
    var loadingView: UIView? {
        return LoadingView(frame: UIScreen.main.bounds)

LH17

protocol ViewStateProtocol: class {
    var stateManager: StateManager? { get }
    
    var loadingView: UIView? { get }
    var errorView: UIView? { get }
    var emptyView: UIView? { get }
    
    var errorMessage: String? { get set }
    func addView(withState state: StatesType)
}