TFL iOS Coding Challenge

A sample app that accesses the TFL REST API at https://api.tfl.gov.uk, and displays statuses for major London roads.

Configuration & build

The app has been built in Xcode 9.3 & Swift 4.1.

The app needs to be configured with API credentials. These need to be put in a Secret.swift file.

1. Clone the repo and copy Secret.swift.example to Secret.swift (the renamed file will be ignored by git), open tfl-app.xcodeproj and ensure that Secret.swift is added to the project, and "Target Membership" is checked for tfl-app.

git clone https://github.com/julesjans/tfl-app.git
cd tfl-app
cp Secret.swift.example Secret.swift

2. Enter relevant credentials in Secret.swift:

enum APICredentials {
    static let app = "Your ApplicationID here"
    static let key = "Your API Key here"
}

3. The project should now build in Xcode, no further dependencies needed.

Overview

tfl-app/

• APIClient - Protocols and class for handling API requests.
• Road - Model definition, complies with protocol for API access.
• Storyboard - View uses Autolayout for a universal iPhone/iPad app.
• ViewController - Controller

tfl-app/Supporting Files

Contains configuration and necessary files for the app to run, also contains seed data for tests, assets and UIColor extension for colours.

Testing

There are two test targets, both of which can be run through the standard test menu functions in Xcode.

1. tfl-appTests/ - standard unit tests for the model and the API. Tests both a mock API and the live API.

2. tfl-appUITests/ - BDD style user story tests, these are tested using the mock API using XCUIApplication launch arguments and dependency injection in the view controller.

Notes

Assumptions

For the purposes of this demo, I have assumed that:

• The app always has network connectivity.

• All roads will have strings for displayName, statusSeverity, statusSeverityDescription & bounds. If either displayName, statusSeverity, statusSeverityDescription are missing the Road object will not be created.

• When a road id is requested, successful reponses from the API are always in the form of a single item array.

• All urls are valid when lowercase and percent-encoded.

Severity Levels

I have taken severity levels from: https://api.tfl.gov.uk/Road/Meta/Severities, which I have then mapped to colours from: http://content.tfl.gov.uk/tfl-colour-standards-issue04.pdf.

Coordinates

To create the map I have used the bounds attribute on the road. The coordinates returned by the API are in the format [Lng, Lat] and therefore the bounds are in the format [West, South, East, North]. I have transposed them to [Lat, Lng] to create bounds of [NorthWest, SouthEast].

The "envelope" attribute contains [Lng, Lat] coordinates plotting a closed path of the bounds with all four corners of the rectangle. I have assumed that this is consistent across all roads, and remains a rectangle, so this can be inferred from the bounds attribute.

Valid roads & alternative version

Using the endpoint: https://api.tfl.gov.uk/road, I have made a feature branch — https://github.com/julesjans/tfl-app/tree/feature/picker — that replaces the text input field with a picker, requesting all the information in one call when the view loads. Using this method ensures that the user cannot enter an invalid road. Tests have been updated on this branch to reflect the changes.