Swift Feature Flags

3. Evaluate flags

import Foundation

class FlagBit {
    static let shared = FlagBit()
    private let sdkKey = ProcessInfo.processInfo.environment["FLAGBIT_SDK_KEY"] ?? ""
    private var cache: [String: Bool] = [:]

    func isEnabled(_ flagKey: String, context: [String: String] = [:]) async -> Bool {
        let cacheKey = "\(flagKey):\(context.hashValue)"
        if let cached = cache[cacheKey] { return cached }

        guard let url = URL(string: "https://flagbit.anethoth.com/api/v1/evaluate") else {
            return false
        }

        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        request.addValue(sdkKey, forHTTPHeaderField: "X-SDK-Key")
        request.httpBody = try? JSONEncoder().encode([
            "flag_key": flagKey,
            "context": context
        ])

        do {
            let (data, _) = try await URLSession.shared.data(for: request)
            let response = try JSONDecoder().decode(FlagResponse.self, from: data)
            cache[cacheKey] = response.value
            return response.value
        } catch {
            return false
        }
    }
}

struct FlagResponse: Decodable { let value: Bool }

// SwiftUI usage
struct ContentView: View {
    @State private var showNewDesign = false

    var body: some View {
        Group {
            if showNewDesign {
                NewDashboardView()
            } else {
                ClassicDashboardView()
            }
        }
        .task {
            showNewDesign = await FlagBit.shared.isEnabled("new-dashboard",
                context: ["user_id": userId, "platform": "ios"])
        }
    }
}

// UIKit usage
class SettingsViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        Task {
            let showBeta = await FlagBit.shared.isEnabled("beta-settings")
            if showBeta {
                addBetaSection()
            }
        }
    }
}