Swift IOS Architecture Quick Start

Constants.swift

//
//  Constants.swift
//  Goomzee
//
//  Created by Michael Sparr on 11/11/15.
//

import Foundation

// MARK: - Environment
struct Environment
{
    static let Development                  = "development"
    static let Test                         = "test"
    static let Stage                        = "stage"
    static let Production                   = "production"
    static let Default                      = "development"
}

// MARK: - Errors & Logging
struct LogLevel
{
    static let Trace                        = "trace"
    static let Debug                        = "debug"
    static let Info                         = "info"
    static let Warn                         = "warn"
    static let Error                        = "error"
    static let Critical                     = "critical"
}

enum InputError: ErrorType
{
    case InputMissing
    case PasswordMismatch
    case InvalidEmail
    ...
}

enum APIError: ErrorType
{
    case ConnectionLost
    case RequestTimeout
    ...
}

enum GeneralError: ErrorType
{
    case IncompleteFeature
    case Unknown
}

// MARK: - Storyboard
struct Storyboard
{
    // storyboard names
    static let Main                         = "Main"
    
    // storyboard IDs
    static let WelcomeViewIdentifier        = "welcomeViewController"
    static let LoginViewIdentifier          = "loginViewController"
    static let RegisterViewIdentifier       = "registerViewController"
    static let ResetPasswordViewIdentifier  = "resetPasswordViewController"
    static let HomeViewIdentifier           = "homeViewController"
    ...
    
    // segues
    static let ShowHomeIdentifier           = "Show Home"
    ...
    
    // collection views
    ...
    
    // table views
    static let BasicCellIdentifier          = "Basic Cell" // generic cell (built-in)
    ...
    
    // generic
    static let EmptyString                  = ""
}

// MARK: - NSUserDefaults
struct Defaults
{
    static let CurrentUserKey               = "myAppUser" // NSUserDefaults object
    ...
}

// MARK: - Images & Files
struct Images
{
    static let DefaultBackground            = "DefaultBackground"
    ...
}

struct FileType
{
    static let PNG                          = "image/png"
    static let JPEG                         = "image/jpeg"
    static let PJPEG                        = "image/pjpeg" // photoshop JPeg
    static let GIF                          = "image/gif"
    static let TIFF                         = "image/tiff"
    static let BMP                          = "image/bmp" // bitmap
    static let SVG                          = "image/svg"
    ...
}
let MimeType = FileType() // alias

// MARK: - Localization
struct Currency
{
    static let USD                          = "USD"
    ...
}

struct Country
{
    static let UnitedStates                 = "US" // ISO standard abbreviation
    ...
}

struct Language
{
    static let EnglishUS                    = "en_US"
    static let EnglishUK                    = "en_UK"
    static let Spanish                      = "es_ES"
    static let French                       = "fr_FR"
    static let German                       = "de_DE"
    static let Greek                        = "gr_GR"
    static let Italian                      = "it_IT"
    ...
}

struct TimeZone
{
    // TODO: determine time zone (name or GMT offsets)
}

// MARK: - AppData & Picklists (dynamic lists)



// MARK: - API
struct API
{
    static let URLS = [
        Environment.Development: "http://localhost:8085/api/v1",
        Environment.Test: "https://dev.yourdomain.com/api/v1",
        Environment.Stage: "https://stage.yourdomain.com/api/v1",
        Environment.Production: "https://yourdomain.com/api/v1"
    ]
    
    static let AllowedFileTypes = [
        FileType.PNG,
        FileType.JPEG,
        FileType.PJPEG,
        FileType.TIFF,
        FileType.BMP,
        FileType.SVG,
        FileType.GIF,
        FileType.SVG,
        FileType.PDF,
        FileType.WAV,
        FileType.MOV
    ]
    
    // constraints
    static let MaxRequestWaitSeconds        = 30 // seconds
    static let MaxUploadSizeMegabytes       = 25 // megabytes
    static let MaxUploadFiles               = 20 // file count
}

Helpers.swift

//
//  Helpers.swift
//  Goomzee
//
//  Created by Michael Sparr on 11/22/15.
//

import Founation
import UIKit

class Helpers
{
    // MARK: - UIAlertViewController (called from UIViewController)
    
    /**
     * Usage: Helpers.showOKAlert("Alert", message: "Something happened", target: self)
     */
    static func showOKAlert(title: String, message: String, target: UIViewController)
    {
        let alertController: UIAlertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        let okAction: UIAlertAction = UIAlertAction(title: Keys.ButtonOK.localized, style: .Default, handler: nil)
        alertController.addAction(okAction)
        target.presentViewController(alertController, animated: true, completion: nil)
    }
    
    /**
     * Usage: Helpers.showOKHelpAlert("Notice", message: "Something happened.", target: self, handler: { (UIAlertAction) -> Void in
     *          // perform help option code here
     *     })
     */
    static func showOKHelpAlert(title: String, message: String, target: UIViewController, handler: ((UIAlertAction) -> Void)?)
    {
        let alertController: UIAlertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        let helpAction: UIAlertAction = UIAlertAction(title: Keys.ButtonHelp.localized, style: .Default, handler: handler)
        let okAction: UIAlertAction = UIAlertAction(title: Keys.ButtonOK.localized, style: .Default, handler: nil)
        alertController.addAction(helpAction)
        alertController.addAction(okAction)
        target.presentViewController(alertController, animated: true, completion: nil)
    }
    
    /**
     * Usage: Helpers.showContinueAlert("Log Out", message: "Are you sure you want to log out?", target: self, handler: { (UIAlertAction) -> Void in
     *          // perform log out code here
     *     })
     */
    static func showContinueAlert(title: String, message: String, target: UIViewController, handler: ((UIAlertAction) -> Void)?)
    {
        let alertController: UIAlertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        let continueAction: UIAlertAction = UIAlertAction(title: Keys.ButtonContinue.localized, style: .Default, handler: handler)
        let cancelAction: UIAlertAction = UIAlertAction(title: Keys.ButtonCancel.localized, style: .Cancel, handler: nil)
        alertController.addAction(cancelAction)
        alertController.addAction(continueAction)
        target.presentViewController(alertController, animated: true, completion: nil)
    }
    
    // MARK: - UIActionSheet (TODO)
    
    // MARK: - Localization
    
    static func getFormattedStringFromNumber(number: Double) -> String 
    {
        let numberFormatter = NSNumberFormatter()
        numberFormatter.numberStyle = .DecimalStyle
        return numberFormatter.stringFromNumber(number)!
    }
    
    static func getFormattedStringFromDate(aDate: NSDate) -> String 
    {
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateStyle = .MediumStyle
        return dateFormatter.stringFromDate(aDate)
    }
    
}

// MARK: - Extensions

extension String 
{
    var localized: String {
        return NSLocalizedString(self, tableName: nil, bundle: NSBundle.mainBundle(), value: "", comment: "")
    }
}

extension String 
{
    func localizedWithComment(comment:String) -> String {
        return NSLocalizedString(self, tableName: nil, bundle: NSBundle.mainBundle(), value: "", comment: comment)
    }
}

Localizable.strings

/* 
  Localizable.strings
  ListIt

  Created by Michael Sparr on 11/22/15.
  Copyright © 2015 Goomzee Corporation. All rights reserved.
*/

// buttons
"button.login"              = "Login";
"button.logout"             = "Log Out";
"button.reset"              = "Reset";
"button.ok"                 = "OK";
"button.help"               = "Help";
"button.cancel"             = "Cancel";
"button.continue"           = "Continue";

// labels
"label.welcome_back"        = "Welcome back,";
"label.password_reset"      = "Password Reset";

// placeholders
"placeholder.email"         = "Email";
"placeholder.password"      = "Password";
"placeholder.confirm"       = "Confirm Password";

// titles
"title.alert"               = "Alert";
"title.notice"              = "Notice";
"title.input_error"         = "Input Error";
"title.missing_fields"      = "Missing Fields";
"title.logout_confirm"      = "Confirm Log Out";
"title.select_option"       = "Select Option";
"title.header"              = "Header";
"title.my_profile"          = "My Profile";
"title.about"               = "About"; // info about the app
"title.help"                = "Help"; // support or help link
"title.logout"              = "Log Out";

// instructions
"info.settings"             = "Welcome back!";

// options

// text
"text.logout_confirm"       = "Are you sure you want to log out?";
"text.fields_required"      = "All fields are required";
"text.password_mismatch"    = "Passwords did not match. Please retry";
"text.unknown_error"        = "An unknown error occurred. Please try again";

LoginViewController.swift

//
//  LoginViewController.swift
//  Goomzee
//
//  Created by Michael Sparr on 11/11/15.
//

import UIKit

class LoginViewController: UIViewController {

    // MARK: - Properties
    
    var user: User!
    var userManager: UserManager!
    
    // MARK: - IBOutlet
    
    @IBOutlet weak var usernameTextField: UITextField!
    @IBOutlet weak var passwordTextField: UITextField!
    
    // MARK: - VC Lifecycle
    
    override func viewDidLoad() {
        super.viewDidLoad()

        userManager = UserManager.sharedInstance // singleton
        
        usernameTextField.placeholder = Keys.PlaceholderUsername.localized
        passwordTextField.placeholder = Keys.PlaceholderPassword.localized
    }

    // MARK: - IBAction
    
    @IBAction func loginAction(sender: AnyObject) {
        
        // perform action
        do {
            let user = try userManager.login(usernameTextField.text!, password: passwordTextField.text!)
            self.performSegueWithIdentifier(Storyboard.ShowHomeIdentifier, sender: user)
        } catch InputError.InputMissing {
            Helpers.showOKAlert(Keys.TitleMissingFields.localized, message: Keys.FieldsRequired.localized, target: self)
        } catch {
            debugPrint(error)
            Helpers.showOKAlert(Keys.TitleAlert.localized, message: Keys.UnknownError.localized, target: self)
        }
        
    }
    
    // MARK: - Navigation

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if let identifier = segue.identifier {
            switch identifier
            {
            case Storyboard.ShowHomeIdentifier:
                // NOTE: - HomeViewController is just custom class for another view after login
                let destinationViewController = segue.destinationViewController as! HomeViewController
                destinationViewController.user = self.user
            default:
                break
            }
        }
    }

}

SettingsTableViewController.swift

//
//  SettingsTableViewController.swift
//  Goomzee
//
//  Created by Michael Sparr on 11/16/15.
//

import UIKit

class SettingsTableViewController: UITableViewController {
    
    // MARK: - Public API
    
    var user: User!
    var userManager: UserManager!
    
    // MARK: - Private
    
    private let settingsNav = [
        [Keys.TitleHeader.localized], // profile image
        [Keys.TitleMyProfile.localized, ...],
        [Keys.TitleAbout.localized, Keys.TitleHelp.localized, Keys.TitleLogout.localized]
    ]
    
    // MARK: - IBOutlet
    
    // MARK: - VC Lifecycle

    override func viewDidLoad() {
        super.viewDidLoad()

        userManager = UserManager.sharedInstance
        user = userManager.getCurrentUser()
    }

    // MARK: - UITableViewDataSource

    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return settingsNav.count
    }

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return settingsNav[section].count
    }
    
    // MARK: - UITableViewDelegate
    
    override func tableView(tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
        if section == 0 {
            return CGFloat.min
        } else {
            return 20.0
        }
    }
    
    override func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        return nil
    }
    
    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        let section = indexPath.section
        let sectionRows = settingsNav[section]
        let row = sectionRows[indexPath.row]
        
        switch row
        {
        case Keys.ButtonLogout.localized:
            Helpers.showContinueAlert(Keys.TitleLogoutConfirm.localized, message: Keys.LogoutConfirm.localized, target: self, handler: { (UIAlertAction) -> Void in
                
                // perform log out
                debugPrint("User logged out at \(NSDate())")
                self.userManager.logout()
                let storyboard: UIStoryboard = UIStoryboard(name: Storyboard.Main, bundle: nil)
                let viewController: UIViewController = storyboard.instantiateViewControllerWithIdentifier(Storyboard.LoginViewIdentifier) as! LoginViewController
                self.presentViewController(viewController, animated: true, completion: nil)
                
            })
        default:
            break
        }
    }
    
    // MARK: - IBAction
    

    // MARK: - Navigation

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if let identifier = segue.identifier {
            debugPrint("Identifier from settings was \(identifier)")
            
            switch identifier {
            case Storyboard.ShowProfileIdentifier:
                debugPrint("Sending user \(user.displayName) to viewController")
                let destinationNavigationController = segue.destinationViewController as! UINavigationController
                let viewController = destinationNavigationController.topViewController as! UserProfileTableViewController
                viewController.user = user
            default:
                break
            }
        }
    }

}

Strings.swift

//
//  Strings.swift
//  Goomzee
//
//  Created by Michael Sparr on 11/22/15.
//

import Foundation

struct Keys
{
    // buttons
    static let ButtonOK                     = "button.ok"
    static let ButtonHelp                   = "button.help"
    static let ButtonCancel                 = "button.cancel"
    static let ButtonContinue               = "button.continue"
    static let ButtonLogin                  = "button.login"
    static let ButtonLogout                 = "button.logout"
    
    // labels
    static let LabelWecomeBack              = "label.welcome_back"
    static let LabelPasswordReset           = "label.password_reset"
    
    // placeholders
    static let PlaceholderEmail             = "placeholder.email"
    static let PlaceholderPassword          = "placeholder.password"
    static let PlaceholderConfirm           = "placeholder.confirm"
    
    // titles
    static let TitleAlert                   = "title.alert"
    static let TitleNotice                  = "title.notice"
    static let TitleInputError              = "title.input_error"
    static let TitleMissingFields           = "title.missing_fields"
    static let TitleLogoutConfirm           = "title.logout_confirm"
    static let TitleHeader                  = "title.header"
    static let TitleMyProfile               = "title.my_profile"
    static let TitleAbout                   = "title.about"
    static let TitleHelp                    = "title.help"
    static let TitleLogout                  = "title.logout"
    
    // instructions
    static let InfoSettings                 = "info.settings"
    
    // options
    
    // text
    static let LogoutConfirm                = "text.logout_confirm"
    static let FieldsRequired               = "text.fields_required"
    static let PasswordMismatch             = "text.password_mismatch"
    static let UnknownError                 = "text.unknown_error"
}

UserManager.swift

//
//  UserManager.swift
//  Goomzee
//
//  Created by Michael Sparr on 11/12/15.
//

import Foundation

struct User
{
    var id: String!
    var displayName: String?
    var emailAddress: String!
}

class UserManager
{
    // MARK: - Singleton
    
    static let sharedInstance = UserManager()
    private init() {
    }
    
    // MARK: - Properties
    
    var user: User!
    
    // MARK: - Public API
    
    func login(username: String?, password: String?) throws -> User
    {
        guard let username = username, let password = password
            where !username.isEmpty && !password.isEmpty else {
                throw InputError.InputMissing
        }
        
        // perform user login functions here
        
        return self.user
    }
    
    func registerUser(username: String?, password: String?, confirm: String?) throws -> User
    {
        guard let username = username, let password = password
            where !username.isEmpty && !password.isEmpty else {
                throw InputError.InputMissing
        }
        guard let confirm = confirm
            where confirm == password else {
                throw InputError.PasswordMismatch
        }
        
        // perform user register functionality here
        
        return self.user
    }
    
    func resetPassword(email: String?) throws
    {
        guard let email = email
            where !email.isEmpty else {
                throw InputError.InputMissing
        }
        
        // perform password reset functionality here
        
    }
    
    // MARK: - Private
    
    ...
}

There are many architectural design patterns at play here so hopefully I can explain some of them. The expectation is you are familiar with Swift and IOS application development so these are merely suggested best practices for assembling your application with proper encapsulation and error handling, plus simplified changes for future IOS updates.

Constants

Setting up a global constants file allows you to take advantage of the built-in code completion in your software editor (i.e. XCode). In addition, you eliminate spelling errors and allow flexibility if things change (change them in one place and not all over your code).

Helpers

Some of the helpers use optional closures handler attribute to allow calling object to execute some code based on user response. This is just a simple example but illustrating how you can centralize common UI events in your app.

Why centralize UI events?

A simple example is when Apple deprecated UIAlertView after iOS8 so any apps that had alerts scattered around their code had to recreate them all to UIAlertController with new syntax. If you used a helper class, then you would just update them in one place and entire app would be compliant.

Singleton

A singleton class is one that is invoked only once and re-used throughout the application. This is a popular pattern but must be used prudently. APIManager, UserManager, SettingsManager are commonly-used singletons that encapsulate the functionality and remote server interaction.

Guard syntax

If you study optionals in Swift you use the if let syntax to handle potential nil return values and prevent exceptions. By using the guard syntax you can control flow of your application and allow the view layer to handle exceptions by using the do ... try ... catch syntax as illustrated in the view controller.

Localization (with i18n)

Updated the files to use localized strings along with helper extension of the String object so you can use String.localized where the string is the key to the Localizable.strings item. Instead of hand-writing each key as used throughout app, instead use a Strings.swift file with Keys struct so you can auto-complete through app.

Adding local strings file:

• File > New > Resource (strings)
• name it Localizable.strings
• tap on file and in Identity inspector tap on "Localize .." button on right and select "English"
• localize your app in base language first, then File > Editor > Add Locales > (desired language)
• export those files to translator and later import into your app

Usage:

• Add string to Localizable.strings file with respective key (don't forget semicolon at end in this file)
• Add key reference to Strings.swift file in appropriate section
• Reference in your code:
  • Keys.SomeConstantName.localized

Note:

XCode has built-in localization of the storyboards, etc. that can generate for each locale and get translated. Minimize the hard-coded strings in your storyboards, however, or override them in code when instantiating your views and leverage this technique wherever possible.