feature-flags

Feature Flag Patterns

Type-Safe Feature Flags

Use enum-based feature flags with protocols for type safety:

// ✅ CORRECT - Type-safe feature flags
protocol FeatureFlag: RawRepresentable where RawValue == String {
    var defaultValue: Bool { get }
    var description: String { get }
}

enum UIFeatureFlag: String, FeatureFlag {
    case newTabPageRedesign = "new_tab_page_redesign"
    case advancedPrivacySettings = "advanced_privacy_settings"
    case voiceSearch = "voice_search"
    case experimentalUI = "experimental_ui"
    
    var defaultValue: Bool {
        switch self {
        case .newTabPageRedesign: return false
        case .advancedPrivacySettings: return true
        case .voiceSearch: return false
        case .experimentalUI: return false
        }
    }
    
    var description: String {
        switch self {
        case .newTabPageRedesign: 
            return "Enable redesigned new tab page"
        case .advancedPrivacySettings: 
            return "Show advanced privacy settings"
        case .voiceSearch: 
            return "Enable voice search functionality"
        case .experimentalUI:
            return "Enable experimental UI components"
        }
    }
}

enum NetworkFeatureFlag: String, FeatureFlag {
    case networkProtectionV2 = "network_protection_v2"
    case enhancedBlocking = "enhanced_blocking"
    
    var defaultValue: Bool {
        switch self {
        case .networkProtectionV2: return false
        case .enhancedBlocking: return true
        }
    }
    
    var description: String {
        switch self {
        case .networkProtectionV2:
            return "Enable Network Protection V2"
        case .enhancedBlocking:
            return "Enhanced content blocking"
        }
    }
}

FeatureFlagger Protocol Implementation

Extend the existing FeatureFlagger with type-safe methods:

// ✅ CORRECT - Type-safe FeatureFlagger extension
extension FeatureFlagger {
    func isEnabled<Flag: FeatureFlag>(_ flag: Flag) -> Bool {
        return isFeatureOn(flag.rawValue) ?? flag.defaultValue
    }
    
    func setEnabled<Flag: FeatureFlag>(_ enabled: Bool, for flag: Flag) {
        setFeatureOn(flag.rawValue, enabled: enabled)
    }
}

// Usage in code
final class FeatureViewModel: ObservableObject {
    private let featureFlagger: FeatureFlagger
    
    init(featureFlagger: FeatureFlagger) {
        self.featureFlagger = featureFlagger
    }
    
    func loadContent() {
        if featureFlagger.isEnabled(UIFeatureFlag.newTabPageRedesign) {
            loadNewDesign()
        } else {
            loadLegacyDesign()
        }
    }
}