/ChatBot

Primary LanguageSwift

Main specs:

  • Developed in SWIFT 2.3

  • iOS 9.0 compatible

  • CocoaPods

  • using VIPER architecture

  • Network requests in the background

  • Network requests recursively repeated if temporary error (increasing delay till 30 second)

  • Network requests applied Apple recommendations (see "Network requests failures" below)

  • Network Log network requests/responses to console with different logs levels

  • Network using HTTPS (see below)

  • Network requests cached (for 10 minutes)

  • Image downloading in the background

  • Unit tests

  • plist with NSAppTransportSecurity

  • plist with UIRequiresPersistentWiFi (like Apple's mail app)

  • Unit tests for Network requests (stubbed with OHHTTPStubs and not stubbed)

  • AutoLayout

  • waiting indicators in status bar / webview

  • Push Notification for implementing slow internet connectivity messaging in the UI

  • using best practices for Date Formatters (PR2Studio/PR2Dates.swift)

  • HeaderDoc HTML based documentation. Generated using jazzy. in docs/swift_output/index.html

  • using SwiftLint to enforce Swift style and conventions

  • using SwiftGen to generate string enums

  • Maximized Xcode Warnings (XcodeWarnings.xcconfig) (http://qualitycoding.org/xcode-warnings)

  • Using as few external libraries as possible:

  • Alamofire

  • AlamofireImage

  • SwiftyJSON

  • SCLAlertView

  • OHHTTPStubs

PR2Studio classes

I applied some of my own classes I use to develop in Swift.

Storyboards

I much prefer to use NIBs than storyboards, storyboards are really a problem in team development (because git conflicts) and with NIBs you have more flexibility to enable different behaviors. But cause the sample provide has Storyboards, I will use them.

I am splitting this in two storyboards (Login and Chat), so this would help in avoiding git merge conflicts and each one will be a VIPER module

SOLID principles

Trying to apply SOLID principles and Clean Code, specially the Single Responsability. Classes must be lightewigth and perform only one task inside his abstraction layer. So it's better to have more classes that one big bloated class

VIPER

This is the first project I do with VIPER, so maybe some things does not follow at full VIPER architecture. Anyhow I understand VIPER as a guideline or concepts to understand, but not to follow at full.

In project root folder there is a PDF who explains my implementation and relarionships between components (VIPER_pablo.pdf)

Reference material:

(Base doc) Architecting iOS Apps with VIPER https://www.objc.io/issues/13-architecture/viper

(I follow this variant) Brigade’s Experience Using an MVC Alternative https://medium.com/brigade-engineering/brigades-experience-using-an-mvc-alternative-36ef1601a41f#.ik6unq2bl

CACHE

I cache network requests, just for showing how can this be done. In a chat is not realistic at all to cache by 10 minutes.

For a chat, network layer should be done in realtime (NodeJS, SignalR, downloadTaskWithRequest of NSURLSession with background session) and also having PushNotifications as failover

Network logger

Logs into the console the network requests and responses. It's instantiated in AppDelegate.swift, here:

PR2Networking.sharedInstance.logLevel = PR2NetworkingLogLevel.PR2NetworkingLogLevelInfo

logLevel can be:

  • PR2NetworkingLogLevelOff - log disabled
  • PR2NetworkingLogLevelDebug - logs full requests and responses
  • PR2NetworkingLogLevelInfo - log with short info
  • PR2NetworkingLogLevelError - logs only when errors

SwiftGen

https://github.com/AliSoftware/SwiftGen

It is used for generating strings enums, so we can avoid the risk of using an non-existing string

Its generated doing this in the console and in the project root folder

swiftgen strings ./ChatBot/Resources/Strings/Localizable.strings --output ./ChatBot/Application/Strings.swift

SwiftLint

https://github.com/realm/SwiftLint

A tool for enforcing good code style.

Install: brew install swiftlint

The run script if deactivated, just in case you don't have it installed. To reenable, uncomment lines in Run Script Phase we have in the ChatBot target

jazzy (Doc generation)

https://github.com/realm/jazzy

jazzy \
  --clean \
  --author PabloRoca \
  --author_url https://pr2studio.com \
  --module-version 1.00 \
  --xcodebuild-arguments -scheme,ChatBotDoc \
  --module ChatBot \
  --output docs/swift_output \
  --min-acl internal

Issues with data

JSON response has no date for every message, so I will put the date when we retrieve the data

Database

I have created this CoreData entities (sqlite tables):

  • CDEUser
  • CDEMessage

They have relationships between then also defined delete rules for them.

Network using HTTPS

Main reasons for using HTTPS is for now, a bit (just a bit more security in network comms) and better speed. See article by Scott Helme why to use HTTPS (https://scotthelme.co.uk/still-think-you-dont-need-https/)

The server is not properly configured for HTTPS (Qualys SSL Test grade B, key exchange using weak Diffie-Hellman (DH), no CSP, no Strict Transport Security (HSTS), Public Key Pins not configured and other security flaws).

If HPKP were configured, I would use SSL Public Key Pinning inestead certificate pinning. I would be using TrustKit (https://github.com/datatheorem/TrustKit) for it. With TrustKit it's easy to enable and avoid a man in the middle attack.

Network requests failures

This is not a trivial issue, some debate ongoing and as per this docs

Networking Overview https://developer.apple.com/library/ios/documentation/NetworkingInternetWeb/Conceptual/NetworkingOverview/WhyNetworkingIsHard/WhyNetworkingIsHard.html#//apple_ref/doc/uid/TP40010220-CH13-SW8

WWDC 2012 Session 706, "Networking Best Practices" https://developer.apple.com/videos/play/wwdc2012-706/

Almofire documentation https://github.com/Alamofire/Alamofire

So we conclude with this (and it is applied in the exercise):

  • Don't use Rechability to determine if a network request should be sent. You should always send the request.
  • Analize Reachability if failures. When Reachability is restored, use the event to retry failed network requests. (Even though the network requests may still fail, this is a good moment to retry them.)
  • Don't timeout, let the system to do it. There is no good timeout value

Current issues (out of time)

  • Autosizing Cells not working. I guess is some autolayout issue.
  • Login Screen. fix landscape orientation

TODO (out of time)

  • complete HeaderDoc documentation.
  • Unit tests for all VIPER elements
  • create secondary target for slow connectivity tests using OHHTTPStubs

To enhance

  • more use of protocols
  • Better CoreData stack
  • move more view logic to presenter? Investigate more View <> Presenter boundaries
  • Better Autolayout