iOS 11 and Swift 4: What Every App Developer Needs to Know

iOS 11 is the biggest developer platform update since Swift was introduced. ARKit, Core ML, Drag and Drop on iPad, the new Files app, and a thoroughly modernised Swift 4 language all land at once. Developers have a lot to absorb — this post distils the essentials.

ARKit: Augmented Reality for Every iPhone 6S and Newer

ARKit uses the iPhone’s camera, gyroscope, and accelerometer to map real-world surfaces and place virtual objects on them — no external sensors required. A basic AR session takes minutes to set up:

import ARKit

class ViewController: UIViewController, ARSCNViewDelegate {
    @IBOutlet var sceneView: ARSCNView!

    override func viewWillAppear(_ animated: Bool) {
        let config = ARWorldTrackingConfiguration()
        config.planeDetection = .horizontal
        sceneView.session.run(config)
    }
}

IKEA Place, Pokémon GO updates, and dozens of retail apps launched ARKit features within weeks of iOS 11’s release — signalling how production-ready it was on day one.

Core ML: On-Device Machine Learning

Core ML lets you run pre-trained machine-learning models directly on the device — no server round-trip, no internet connection required. Convert any TensorFlow, Keras, or scikit-learn model to the .mlmodel format with coremltools, drag it into Xcode, and get a generated Swift class with a few lines of inference code.

Swift 4: Codable — Bye-Bye Manual JSON Parsing

Swift 4’s most beloved addition is the Codable protocol (a typealias for Encodable & Decodable). Define a struct that matches your JSON and let the compiler generate all the parsing code:

struct User: Codable {
    let id: Int
    let name: String
    let email: String
}

let json = Data("""{ "id": 1, "name": "Alice", "email": "alice@example.com" }""".utf8)
let user = try JSONDecoder().decode(User.self, from: json)
print(user.name) // Alice

Drag and Drop (iPad)

iOS 11 brings system-wide Drag and Drop to iPad. Apps adopt it via the UIDragInteraction and UIDropInteraction APIs. TableView and CollectionView have built-in drag-and-drop support.

String Improvements in Swift 4

Strings are back to being a Collection of Character values, multi-line string literals use triple quotes """, and substring handling no longer requires a String() initialiser at every turn.

iOS 11 is a landmark release. ARKit and Core ML alone open entirely new categories of apps. Start experimenting with both now — users will reward the creativity.