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🏇🏼 Next To Go

An app made with ❤️ to demonstrate some examples of clean architecture, code organisation, loose coupling, unit testing, accessibility and some of the best practices used in modern iOS programming using Swift & SwiftUI

📱 App Goal

Create an iOS app that displays Next to Go races using Neds free public API. A user should always see top 5 races, and they should be sorted by time ascending. Race should disappear from the list after 1 min past the start time. Take some inspirations from popular betting apps like Neds, Ladbrokes, Sportsbet etc.

💼 Requirements

  1. As a user, I should be able to see a time ordered list of races ordered by advertised start ascending
  2. As a user, I should not see races that are one minute past the advertised start
  3. As a user, I should be able to filter my list of races by the following categories: Horse, Harness & Greyhound racing
  4. As a user, I can deselect all filters to show the next 5 from of all racing categories
  5. As a user, I should see the meeting name, race number and advertised start as a countdown for each race.
  6. As a user, I should always see 5 races and data should automatically refresh

👨🏽‍💻 Solution Approach

Before we move onto breaking down the app layers and architecture, let's read some of the best practices and how other SwiftUI developers in the community are feeling about various ways to architect a scalable app.

This article on clean-architecture-swiftui summarises the story quite well 🙏🏽

Clean Architecture with MVVM

After reading it, I made this following decisions to go ahead and use some aspects of the VIPER pattern and mixing in with MVVM while still having core concepts of clean architecture from uncle Bob 🧔🏼‍♂️.

Codebase is broken down into 4 logical layers (via Swift Packages)

  • DataLayer:

    • Network fetching of raw data and JSON decoding via URL, error code mapping etc.

  • DomainLayer:

    • Business logic of polling and combining data based on filters, sorting of top 5 based on timing etc.
    • Interactors live here. (aka. UseCase in some codebases)

  • PresentationLayer:

    • Domain data to SwiftUI binding logic
    • All UI specific code (SwiftUI OR UIKit)

  • SharedUtils:

    • Common light weight utility helpers and extensions

  • A mix of MVVM and VIPER design pattern is used to achieve loose coupling and unit testing via Dependency Injection patterns and mocks

  • Currently use Apple's Combine based Reactive Binding

  • ✋🏽TODO: Migrate from Combine driven Publishers into Swift's Modern Concurrency Async Await paradigm (layer by layer where feasible and makes sense)

  • Unit Testing (about 70%) has been covered on each layer. (More being added iteratively...)

  • Some TODO notes left in the code deliberately for potential improvements and SwiftLint warns us about those to trace them

  • To achieve the requirement 2 above, use ⏰ hard negative tolerance in the interactor (currently set at -90 seconds). This can be configured to show more old races which are past few minutes with negative countdown timer on the UI. Configurable option in the app logic. 🤓

🏹 Next Steps (TODO) 🏹

The package dependencies (import logic from one to another) are shown below:

  graph TD;
      A[Presentation Layer] --> B[Domain Layer];
      B-->C[Data Layer];
      A-.->C;
      A-->D[Shared Utils];
      B-->D;
      C-->D;
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Please refer from the project navigator in Xcode to see the layering.

Project Targets Tests

The overall summary in terms of UML

sequenceDiagram
    participant  RaceItemCellUI
    participant RaceListUI
    participant ViewModel
    participant Interactor
    participant NetworkService
    participant URLSession

    RaceListUI->>ViewModel: Reactively bound to viewModel's response
    
    ViewModel->>Interactor: Get the desired lists of Race domain models (reactively)
    loop Polling
        Interactor->>Interactor: Every 5 min to get the full list from Network
    end
    loop Polling
        Interactor->>Interactor: Every 50 sec to sort the latest on top and discard older races
    end

    Interactor->>NetworkService: Get the full max list of RaceSummary data models
    NetworkService->>URLSession: Get the full raw JSON data as HTTP request
    URLSession->>NetworkService: HTTP response body
    loop Mapping
        NetworkService->>NetworkService:  Apply custom JSON decoding into data models and error mapping
    end

    NetworkService->>Interactor: full List of RaceSummary every 5 min
    Interactor->>ViewModel: Latest sorted list of domain models every 50 sec (reactively)

    ViewModel->>RaceListUI: Pass back list of RaceItemViewModels
    loop Transformation
        ViewModel->>ViewModel: Transform & cook raw domain level data into UI friendly RaceItemViewModel
    end

   RaceListUI->>RaceItemCellUI: SwiftUI binding of RaceItemViewModel
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graph TB
    subgraph DataLayer;
    a2[URLSession]-. RaceSummary Data Model .->a1[NetworkService];
    end;
    subgraph DomainLayer;
    a1-. applies some business logic  .->b1[Interactor];
    end;
    subgraph PresentationLayer;
    c1[NextToGoViewModel]-. list of RaceItemViewModel reactively .->c2[Races List UI];
    c2-. RaceItemViewModel .->c3[Races Cell Item UI];
    c1-. list of FilterModels .->c4[FilterViewModel];
    c4-. applies to .->c1;
    end;
    b1-. list of Race Domain Model reactively .->c1;
    c1-. Category filters .->b1;
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💻 Installation

  • Xcode 14 or later (required)
  • Clean build /DerivedData folder if any
  • Let the Swift package Manager load and sync
  • Build the project and let the Swift Package Manager pulls the remote SwiftLint plugin
  • iOS 15 minimum support (SwiftUI v4 used)
  • If you're testing on a device, select automatically manage signing options
  • 💗 Please 🙏🏽 test on a real iPhone to play with the Haptics feedbacks added :) 💗

♿️ Accessibility

  • Each elements on the app are fully VoiceOver compatible (Test on a device to hear the sounds)
  • Some Text elements have been combined to give overall accessibility label (icons are excluded)
  • Custom accessibility hints are also applied to buttons (eg. Filters)
  • Filters do announce the VoiceOver labels for visually impaired users, and updates their traits between button and selected
  • All texts on UI can grow with system level font scaling and auto reposition themselves when needed to fit better within the container
  • UI also adapts to layout changes - landscape / portrait modes (including iPad support)

🚀 Extra Features

  • A settings more menu has been made to show extra info and author attribution and demonstrate how easy & fast SwiftUI is to build such layouts
  • Some custom SwiftUI animations are applied to many icons (all SFSymbols and some custom made SF symbol such horse, harness etc.)
  • Dark mode toggle can be applied from Settings (there is a minor 🐞 bug there now, after applying this, shimmers go funny and does not update, app kill and restart needed)
  • Loading shimmers are added when refreshing races & changing between race category filters
  • User should be able to filter out top number desired (eg, 5, 10, 20) races and also filter based on a specific country

⛈️ Error Handling UX

  • Custom error UI is shown when loading error occurs
  • NetworkFailure (i.e. internet disconnected) shows its custom message and animated icon
  • All other server errors have a generic message and animated icon
  • If no races are found from API for some odd reason, then empty state also shows with some messaging

Screenshots

Filtering Races Settings

Errors (Test steps included)

Empty State Generic Sever Error Internet Lost Error
Update code in NextRacesInteractor.swift to return [] by commenting out results.append(..) statement around line 65 Update the API endpoint in ApiConstants to something incorrect URL Disconnect WiFi & connect back and test
Dark modes

🚀 NEW FEATURES (added recently)

Country Selection Top Races Count Selection
Combined Filters Effect Reset Filters

Accessibility

Dynamic Font Scaling
🎧 VoiceOver 📢 Labels and Traits & sounds 🎼

📢 Play with the mov videos below to see VoiceOver in action

  • Turn the sounds ON within the player (default muted)
a11y-voiceover-soundsp-part-1.mov
a11y-voiceover-soundsp-part-2.mov
Portrait Large Landscape Large