MAFSegueHandlerType: This protocol implements best Swift practices to simplify the use of segues throuhout the app

MAFSegueHandlerType.swift

//
//  MAFSegueHandlerType.swift
//  MAFFinance
//
//  Created by Miguel Fermin on 8/1/15.
//  Copyright © 2015 Miguel Fermin. All rights reserved.
//

import UIKit

/// Provides convenient syntax to work with storyboard segues.
///
/// This protocol implements best Swift practices to simplify the use of segues throuhout the app.
/// Benefits of using this approach:
/// * Compiler errors when adding new segues if the new case isn't handled
/// * Reusable
/// * Convenient syntax
/// * Tighen app constrains using protocols with associate types
/// * Share implementation through a constrained protocol extension
protocol MAFSegueHandlerType {
    typealias MAFSegueIdentifier: RawRepresentable
}

extension MAFSegueHandlerType where Self: UIViewController, MAFSegueIdentifier.RawValue == String {
    /// Initiates the segue with the specified MAFSegueIdentifier from the current view controller'€™s storyboard file.
    ///
    /// This method wraps UIViewControlle's **"performSegueWithIdentifier:sender:"** method but uses the convenient MAFSegueIdentifier to
    /// provide a concise syntax and be reusable throughout the app.
    /// - parameter segueIdentifier: The MAFSegueIdentifier enum type that identifies the triggered segue.
    /// - parameter sender: The object that you want to use to initiate the segue. This object is made available for informational purposes during the actual segue.
    func performSegueWithIdentifier(segueIdentifier: MAFSegueIdentifier, sender: AnyObject?) {
        performSegueWithIdentifier(segueIdentifier.rawValue, sender: sender)
    }
    
    /// Extracts the passed segue's identifier, wraps it in a MAFSegueIdentifier enum type, and returns it.
    /// - parameter segue: The segue to extract the **segue.identifier** from.
    /// - returns: A MAFSegueIdentifier enum type representing the segue's identifier.
    func segueIdentifierForSegue(segue: UIStoryboardSegue) -> MAFSegueIdentifier {
        guard let identifier = segue.identifier, let segueIdentifier = MAFSegueIdentifier(rawValue: identifier)
            else { fatalError("Invalid segue identifier \(segue.identifier)") }
        return segueIdentifier
    }
    
    /// Gets and returns the segue's destination UINavigationController's topViewController.
    /// - important: This method should only be used when you want the modalPresentationStyle set to **CurrentContext** on iPad.
    /// - parameter segue: The segue to get the navigation controller's topViewController from.
    /// - returns: The segue's destination UINavigationController's topViewController.
    func navigationTopViewControllerFromSegue(segue: UIStoryboardSegue) -> UIViewController {
        let navigationController = (segue.destinationViewController as! UINavigationController)
        // Set the modalPresentationStyle to CurrentContext on iPad only. If this is set on iPhone,
        // the keyboard would cover the textfields positioned at the lower side of the screen.
        if (UIDevice.currentDevice().userInterfaceIdiom == UIUserInterfaceIdiom.Pad) {
            navigationController.modalPresentationStyle = UIModalPresentationStyle.CurrentContext
        }
        return navigationController.topViewController!
    }
}


/* How to use it */

// Conform to "MAFSegueHandlerType" in your view controller
class MAFViewController: MAFDetailViewController, MAFSegueHandlerType {... }

// Then you must implement the "MAFSegueIdentifier" enum as follows:
enum MAFSegueIdentifier: String {
    case ShowJobEditor    = "ShowJobEditor"
    case ShowAddPaycheck  = "ShowAddPaycheck"
    case ShowAllPaychecks = "ShowAllPaychecks"
}
  
// Notice that "ShowJobEditor", "ShowAddPaycheck", and "ShowAllPaychecks" should be set on a storyboard
// This leads to the following prepareForSegue implementation:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    switch segueIdentifierForSegue(segue) {
    case .ShowJobEditor:
        // Config...
    case .ShowAddPaycheck:
        // Config...
    case .ShowAllPaychecks:
        // Config...
    }
}