How to use Firebase RemoteConfig

Issue #493

Declare in Podfile

pod 'Firebase/Core'
pod 'Firebase/RemoteConfig'

Use RemoteConfigHandler to encapsulate logic. We introduce Key with CaseIterable and defaultValue of type NSNumber to manage default values.

import Firebase
import FirebaseRemoteConfig

final class RemoteConfigHandler {
    let remoteConfig: RemoteConfig

    enum Key: String, CaseIterable {
        case interval = "fetch_interval"

        var defaultValue: NSNumber {
            switch self {
            case .periodicGetSalons: return NSNumber(value: 300)
            }
        }
    }

    init() {
        self.remoteConfig = RemoteConfig.remoteConfig()

        let settings = RemoteConfigSettings()
        settings.minimumFetchInterval = 0
        self.remoteConfig.configSettings = settings

        let map = Key.allCases.reduce([String: NSObject](), { map, key in
            var map = map
            map[key.rawValue] = key.defaultValue
            return map
        })

        self.remoteConfig.setDefaults(map)
    }

    func update()  {
        self.remoteConfig.fetchAndActivate(completionHandler: { status, error in
            print(status, error as Any)
        })
    }

    var fetchInterval: TimeInterval {
        return getValue(key: .interval, transform: { $0.doubleValue })
    }

    private func getValue<T>(key: Key, transform: (NSNumber) -> T) -> T {
        let number = remoteConfig.configValue(forKey: key.rawValue).numberValue ?? key.defaultValue
        return transform(number)
    }
}