I'm developing an app that joins tele-conference calls so we use conference numbers a lot. I've got this basic structure to encapsulate the information regarding a conference number.

///A model that represents a teleconference number.
struct ConferenceNumber 

 let iso : String ///Interntational Standardised 2 letter Abbreviation for country.
 let conferenceProvider: ConferenceProvider ///The company that hosts the conference call the number is for.
 let number : String ///The phone number
 let toll : Bool ///Whether the number is a paid or free line.
 let country: String

 init(ISO: String, country: String, number:String, provider: ConferenceProvider, toll: Bool)
 self.iso = ISO
 self.country = ConferenceNumber.localeName(from: ISO) ?? country
 self.number = number
 self.conferenceProvider = provider
 self.toll = toll
 

I'm running in to two problems:

1. This class if often bypassed in favour of storing the numbers in [String] arrays. I can't think of a nice way to put this in to an object as ConferenceNumber.number doesn't sound right.




2. The conferenceProvider property has resulted in over a dozen switch statement in our code base which all look similar to the code below. Is it possible to reduce repeating myself this often with protocols or subclasses?

ConferenceProvider enum

///Defines the type of conference call service the meeting uses if any.
public enum ConferenceProvider : String 
 case unknown = "",
 zoom = "Zoom",
 att = "AT&T",
 webex = "WebEx",
 arkadin = "Arkadin"

Class with ConferenceProvider switch statements example

import Foundation

///Builds, stores, retrieves and queries conference number directories.
class ConferenceNumberDirectory 

 static let att: [ConferenceNumber] = 
 return buildDirectory(for: .att, from: jsonArray)
 ()

 static let arkadinMeetings: [ConferenceNumber] = 
 return buildDirectory(for: .arkadinMeetings, from: jsonArray)
 ()

 static let webex: [ConferenceNumber] = 
 return buildDirectory(for: .webex, from: jsonArray)
 ()

 static let zoom: [ConferenceNumber] = 
 return buildDirectory(for: .zoom, from: jsonArray)
 ()

 static let allProviders: [ConferenceNumber] = 
 return att + arkadinMeetings + webex + zoom
 ()

 static let attPhoneNumbers: [String] = 
 return ConferenceNumberDirectory.att.map( $0.number )
 ()

 static let arkadinMeetingsPhoneNumbers: [String] = 
 return ConferenceNumberDirectory.arkadinMeetings.map( $0.number )
 ()

 static let webexPhoneNumbers: [String] = 
 return ConferenceNumberDirectory.webex.map( $0.number )
 ()

 static let zoomPhoneNumbers: [String] = 
 return ConferenceNumberDirectory.zoom.map( $0.number )
 ()

 static let allPhoneNumber: [String] = 
 return ConferenceNumberDirectory.allProviders.map $0.number 
 ()

 private static let jsonArray: [Any]? = 
 guard let numbersFilePath = Bundle.main.path(forResource: "numbers", ofType:"json") else 
 return nil
 

 let data = try! Data(contentsOf: URL(fileURLWithPath:numbersFilePath), options: .uncached)

 return try! JSONSerialization.jsonObject(with: data) as? [Any]
 ()

 ///Takes the outputted [Any]? from a JSON file and builds an Array of ConferenceNumber objects suitable for Call In to use.
 static func buildDirectory(for conferenceProvider: ConferenceProvider, from jsonArray: [Any]?) -> [ConferenceNumber] 
 var directory = [ConferenceNumber]()
 do 
 guard let rootJSONArray = jsonArray else 
 throw SerializationError.missing("JSON Root")
 

 for entry in rootJSONArray 
 guard let dictionary = entry as? [String: Any] else 
 throw SerializationError.missing("JSON Root")
 
 guard let isoCode = dictionary["ISO Code"] as? String else 
 throw SerializationError.missing("isoCode")
 
 guard let country = dictionary["Country"] as? String else 
 throw SerializationError.missing("country")
 

 if let key = getTollKey(for: conferenceProvider), let tollNumbers = try self.extractNumbers(from: dictionary, forKey: key) 
 directory.append(contentsOf: tollNumbers.mapConferenceNumber(ISO: isoCode, country: country, number: $0, provider: conferenceProvider, toll: true) )
 
 if let key = getTollFreeKey(for: conferenceProvider), let tollFreeNumbers = try self.extractNumbers(from: dictionary, forKey: key) 
 directory.append(contentsOf: tollFreeNumbers.mapConferenceNumber(ISO: isoCode, country: country, number: $0, provider: conferenceProvider, toll: false))
 
 
 
 catch let error 
 print(error)
 
 return directory
 

 ///Returns the directory for a given conference provider. Returns all if no numbers exist for this provider.
 static func getDirectory(for conferenceProvider: ConferenceProvider) -> [ConferenceNumber]? 
 switch conferenceProvider 
 case .arkadinMeetings:
 return ConferenceNumberDirectory.arkadinMeetings
 case .att:
 return ConferenceNumberDirectory.att
 case .webex:
 return ConferenceNumberDirectory.webex
 case .zoom:
 return ConferenceNumberDirectory.zoom
 default:
 return ConferenceNumberDirectory.att + ConferenceNumberDirectory.arkadinMeetings + ConferenceNumberDirectory.webex + ConferenceNumberDirectory.zoom
 
 

 /**
 Returns a ConferenceNumber that matches the phone number and the country ISO code provided. Returns nil if no number is found.
 - parameter number: The phone number to try and find a match for
 - parameter isoCode: The international standard organizations 2 digit code that represents a country for all known languages

 At present we do not store ConferenceNumber Objects in the settings so we often need to convert the Strings we store back in to their original conference number. Where we to save the object we would still need this as user entered numbers will not contain all ConferenceNumber properties.
 */
 static func findConferenceNumber(usingNumber number: String, andISOCode isoCode: String?, fromDirectory conferenceProvider: ConferenceProvider = .unknown) -> ConferenceNumber? 

 if number.isEmpty 


 /** 
 Returns all conference numbers that share the same number.
 Similarly as the previous one, findConferenceNumber() but getting all possibilities because we know that some countries share the same number, example: 8884266840
 */
 static func findConferenceNumbers(usingNumber number: String, fromDirectory conferenceProvider: ConferenceProvider? = .unknown) -> [ConferenceNumber] 

 if number.isEmpty 
 return 
 

 switch conferenceProvider 
 case .att?:
 return ConferenceNumberDirectory.att.filter( $0.number == number)
 case .arkadinMeetings?:
 return ConferenceNumberDirectory.arkadinMeetings.filter($0.number == number)
 case .webex?:
 return ConferenceNumberDirectory.webex.filter( $0.number == number)
 case .zoom?:
 return ConferenceNumberDirectory.zoom.filter($0.number == number)
 default:
 let allConferenceNumbers = ConferenceNumberDirectory.att + ConferenceNumberDirectory.arkadinMeetings + ConferenceNumberDirectory.webex + ConferenceNumberDirectory.zoom
 return allConferenceNumbers.filter($0.number == number)
 
 

 ///Find the provider for a given number, return unknown if the number does not exist
 ///- warning: This will return the first provider that has the current number seeing as providers don't share numbers.
 static func findProvider(forNumber queriedNumber: String) -> ConferenceProvider 
 return ConferenceNumberDirectory.allProviders.first $0.number == queriedNumber ?.conferenceProvider ?? .unknown
 

 ///Returns an array of all country iso codes a queriedNumber is used by.
 static func findCountryISOCodes(forNumber queriedNumber: String) -> [String] 
 return ConferenceNumberDirectory.allProviders.filter $0.number == queriedNumber .map( $0.iso )
 


 ///Extracts telephone numbers from a given dictionary and key by taking the value as a string then returning an array of each comma seperated component of that string.
 private static func extractNumbers(from dictionary: [String: Any], forKey key: String?) throws -> [String]? 
 guard let jsonKey = key ,let tollNumbersString = dictionary[jsonKey] as? String else 
 throw SerializationError.missing(key ?? "key is nil")
 
 if tollNumbersString.isEmpty 
 return nil
 
 return tollNumbersString.components(separatedBy: ",")
 

 ///Returns the JSON key to access a given ConferenceProviders toll numbers.
 private static func getTollKey(for provider: ConferenceProvider) -> String? 
 switch provider 
 case .att:
 return "AT&T toll"
 case .arkadinMeetings:
 return "arkadin Meetings toll"
 case .webex:
 return "Webex toll"
 case .zoom:
 return "Zoom toll"
 default:
 return nil
 
 

 ///Returns the JSON key to access a given ConferenceProviders toll-free numbers.
 private static func getTollFreeKey(for provider: ConferenceProvider) -> String? 
 switch provider 
 case .att:
 return "AT&T toll-free"
 case .arkadinMeetings:
 return "arkadin Meetings toll-free"
 case .webex:
 return "Webex toll-free"
 default:
 return nil
 
 

Class with ConferenceProvider switch statements Example 2

/// Data class, responsible for storing and retrieving of user settings.

import Foundation

class Settings 
 /// init user defaults with the app group suite to be able to use the same values in the app and in the widget
 static let defaults = SharedGlobals.appGroupDefaults

 static var id: String? 
 get return self.defaults.string(forKey: "id") 
 set self.defaults.set(newValue, forKey: "id") 
 

 static var attNumber: String? 
 get return self.defaults.string(forKey: "attNumber") 
 set self.defaults.set(newValue, forKey: "attNumber") 
 

 static var attCountry: String? 
 get return self.defaults.string(forKey: "attCountry") 
 set self.defaults.set(newValue, forKey: "attCountry") 
 

 static var attISO: String? 
 get return self.defaults.string(forKey: "attISO") 
 set self.defaults.set(newValue, forKey: "attISO") 
 

 static var attHostCodes: [String] 
 get if let codes = self.defaults.stringArray(forKey: "hostCodes")
 return codes
 else 
 return 
 
 
 set self.defaults.set(newValue, forKey: "hostCodes") 
 

 ///AT&T participant codes, these are paired to hostcodes (by index) so we can determine which host code to use via parsed participant codes.
 static var attParticipantCodes: [String] 
 get if let codes = self.defaults.stringArray(forKey: "participantCodes")
 return codes
 else 
 return 
 
 
 set self.defaults.set(newValue, forKey: "participantCodes") 
 

 ///arkadinMeetings (Smartcloud)
 static var arkadinMeetingsCountry: String? 
 get return self.defaults.string(forKey: "arkadinMeetingsCountry") 
 set self.defaults.set(newValue, forKey: "arkadinMeetingsCountry") 
 


 static var arkadinMeetingsNumber: String? 
 get return self.defaults.string(forKey: "arkadinMeetingsNumber") 
 set self.defaults.set(newValue, forKey: "arkadinMeetingsNumber") 
 

 static var arkadinMeetingsISO: String? 
 get return self.defaults.string(forKey: "arkadinMeetingsISO") 
 set self.defaults.set(newValue, forKey: "arkadinMeetingsISO") 
 


 static var arkadinMeetingsModeratorCode: String? 
 get return self.defaults.string(forKey: "arkadinMeetingsModeratorCode") 
 set self.defaults.set(newValue, forKey: "arkadinMeetingsModeratorCode") 
 


 ///WEBEX
 static var webexNumber: String? 
 get return self.defaults.string(forKey: "webexNumber") 
 set self.defaults.set(newValue, forKey: "webexNumber") 
 

 static var webexCountry: String? 
 get return self.defaults.string(forKey: "webexCountry") 
 set self.defaults.set(newValue, forKey: "webexCountry") 
 

 static var webexISO: String? 
 get return self.defaults.string(forKey: "webexISO") 
 set self.defaults.set(newValue, forKey: "webexISO") 
 

 //Webex participant code, this is stored as the participant code is required to dial in even when the user is hosting.
 static var webexAccessCode: String? 
 get return self.defaults.string(forKey: "webexAccessCode") 
 set self.defaults.set(newValue, forKey: "webexAccessCode") 
 

 static var webexHostPin: String? 
 get return self.defaults.string(forKey: "webexHostPin") 
 set self.defaults.set(newValue, forKey: "webexHostPin") 
 


 ///ZOOM
 static var zoomNumber: String? 
 get return self.defaults.string(forKey: "zoomNumber") 
 set self.defaults.set(newValue, forKey: "zoomNumber") 
 

 static var zoomCountry: String? 
 get return self.defaults.string(forKey: "zoomCountry") 
 set self.defaults.set(newValue, forKey: "zoomCountry") 
 

 static var zoomISO: String? 
 get return self.defaults.string(forKey: "zoomISO")
 set self.defaults.set(newValue, forKey: "zoomISO")
 

 static var zoomMeetingId: String? 
 get return self.defaults.string(forKey: "zoomMeetingId") 
 set self.defaults.set(newValue, forKey: "zoomMeetingId") 
 


 // MARK: User

 ///Country
 static var country: String? 
 get return self.defaults.string(forKey: "country") 
 set self.defaults.set(newValue, forKey: "country") 
 

 static var email: String? 
 get return self.defaults.string(forKey: "email") 
 set self.defaults.set(newValue, forKey: "email") 
 

 ///Return the user's name. If this hasn't been saved extract their name from their arkadin calendar and save it.
 static var usersName: String? 

 if let savedName = defaults.string(forKey: "name") 
 return savedName
 

 if let calendar = MeetingsFetcher().getarkadinCalendar().first,
 let parsedName = calendar.title.parseFirstMatch(from: Regex.organizerNameFromEKCalendar)
 
 defaults.set(parsedName, forKey: "name")
 return parsedName
 
 return AppConfigInteractor.getUserName()
 

 static var callMethod: String 
 get 
 if let method = self.defaults.string(forKey: "callMethod") 
 return method
 else 
 return CallMethod.methods.device.rawValue
 
 
 set self.defaults.set(newValue, forKey: "callMethod") 
 

 ///VIPS: email + relation for a max of 9 VIPs
 static var VIPemails: [String] 
 get if let vips = self.defaults.stringArray(forKey: "VIPemails") 
 return vips
 else 
 return 
 
 
 set self.defaults.set(newValue, forKey: "VIPemails") 
 

 static var VIPnames: [String] 
 get if let vips = self.defaults.stringArray(forKey: "VIPnames") 
 return vips
 else 
 return 
 
 
 set self.defaults.set(newValue, forKey: "VIPnames") 
 

 static var VIPrelations: [String] 
 get if let vips = self.defaults.stringArray(forKey: "VIPrelations")
 return vips
 else 
 return 
 
 
 set self.defaults.set(newValue, forKey: "VIPrelations") 
 


 ///notification
 static var notificationsAllowed: Bool 
 get return self.defaults.bool(forKey: "notification") 
 set self.defaults.set(newValue, forKey: "notification") 
 

 ///location awareness
 static var locationAwarenessAllowed: Bool 
 get return self.defaults.bool(forKey: "locationAwareness") 
 set self.defaults.set(newValue, forKey: "locationAwareness") 
 

 ///promt for authentication awareness
 static var promptForAuthentication: Bool 
 get return self.defaults.bool(forKey: "promptForAuthentication") 
 set self.defaults.set(newValue, forKey: "promptForAuthentication") 
 

 ///last time the user was prompt for authentication
 static var lastAuthenticationPromptDate: Date? 
 get return self.defaults.object(forKey: "lastAuthenticationPromptDate") as? Date 
 set self.defaults.set(newValue, forKey: "lastAuthenticationPromptDate") 
 

 ///audiosummary
 static var audioSummary: Bool 
 get return self.defaults.bool(forKey: "audioSummary") 
 set self.defaults.set(newValue, forKey: "audioSummary") 
 


 /// Local settings (not stored in the cloud)

 static var notifyNumberOfMinutesBeforeEvent: Double 
 get return self.defaults.double(forKey: "notifyNumberOfMinutesBeforeEvent") 
 set self.defaults.set(newValue, forKey: "notifyNumberOfMinutesBeforeEvent") 
 

 static var landingPageWasReadToday: Bool 
 get return self.defaults.bool(forKey: "landingPageWasReadToday") 
 set self.defaults.set(newValue, forKey: "landingPageWasReadToday") 
 

 static var lastDayAudioWasRead: Int 
 get return self.defaults.integer(forKey: "lastDayAudioWasRead") 
 set self.defaults.set(newValue, forKey: "lastDayAudioWasRead") 
 

 static var lastDayPopUpWasDismissed: Int 
 get return self.defaults.integer(forKey: "lastDayPopUpWasDismissed") 
 set self.defaults.set(newValue, forKey: "lastDayPopUpWasDismissed") 
 

 static var meetingsDismissed: [String] 
 get if let meetings = self.defaults.stringArray(forKey: "meetingsDismissed") 
 return meetings
 else 
 return 
 
 
 set self.defaults.set(newValue, forKey: "meetingsDismissed") 
 

 static var promptToModifyNumber: Bool 
 get return self.defaults.bool(forKey: "promptToModifyNumber") 
 set self.defaults.set(newValue, forKey: "promptToModifyNumber") 
 

 ///returns true if the user has already gone though the onboarding process
 static var didOnboarding: Bool 
 get return self.defaults.bool(forKey: "didOnboarding") 
 set self.defaults.set(newValue, forKey: "didOnboarding") 
 

 static var advancedParticipantCode: String 
 get 
 if let code = self.defaults.string(forKey:"advancedParticipantCode") 
 return code
 else 
 return SharedGlobals.Call.DEFAULT_PARTICIPANT_CODE
 
 
 set self.defaults.set(newValue, forKey: "advancedParticipantCode") 
 

 static var advancedHostCode: String 
 get 
 if let code = self.defaults.string(forKey:"advancedHostCode") 
 return code
 else 
 return SharedGlobals.Call.DEFAULT_HOST_CODE
 
 
 set self.defaults.set(newValue, forKey: "advancedHostCode") 
 

 static var advancedNoCode: String 
 get 
 if let code = self.defaults.string(forKey: "advancedNoCode") 
 return code
 else 
 return SharedGlobals.Call.DEFAULT_NO_CODE
 
 
 set self.defaults.set(newValue, forKey: "advancedNoCode") 
 

 static var versionID: String? 
 get return self.defaults.string(forKey: "versionID") 
 set self.defaults.set(newValue, forKey: "versionID") 
 

 static var buildID: String? 
 get return self.defaults.string(forKey:"buildID") 
 set self.defaults.set(newValue, forKey: "buildID") 
 

 ///always use conference number and ignore number in invitation
 static var prioritizeSettingsNumbers: Bool 
 get return self.defaults.bool(forKey: "prioritizeSettingsNumbers") 
 set self.defaults.set(newValue, forKey: "prioritizeSettingsNumbers") 
 

 ///Returns the settings number for a given provider or the AT&T number if provider is unknown.
 static func phoneNumber(for provider: ConferenceProvider) -> String? 
 switch provider 
 case .unknown:
 return attNumber ?? webexNumber ?? arkadinMeetingsNumber ?? zoomNumber
 case .att:
 return attNumber
 case .arkadinMeetings:
 return arkadinMeetingsNumber
 case .webex:
 return webexNumber
 case .zoom:
 return zoomNumber
 
 

 ///Returns the iso code for the current Settings number of a given provider, returns nil if no settings number is set.
 static func isoCodeForSettingsNumber(with provider: ConferenceProvider) -> String? 
 switch provider 
 case .unknown:
 return nil
 case .att:
 return attISO
 case .arkadinMeetings:
 return arkadinMeetingsISO
 case .webex:
 return webexISO
 case .zoom:
 return zoomISO
 
 

 /**
 Returns the participant codes for a given provider

 - Note: Returns an empty array for arkadinMeetings as we don't store these participant codes.
 - Note: For unknown providers this returns the participant codes for all meetings other than AT&T
 as the user is unlikely to ever dial in with their own AT&T participant code (they'd use their host code).
 */
 static func participantCodes(for provider: ConferenceProvider) -> [String] 
 switch provider 
 case .unknown:
 return [webexAccessCode, zoomMeetingId].flatMap$0
 case .att:
 return attParticipantCodes
 case .arkadinMeetings:
 return 
 case .webex:
 return [webexAccessCode].flatMap$0
 case .zoom:
 return [zoomMeetingId].flatMap$0
 
 

 /**
 Returns the host codes for a given provider

 - Note: Returns an empty array for zoom conference calls as they have no host codes.
 - Note: For unknown providers this returns all hostcodes
 */
 static func hostCodes(for provider: ConferenceProvider) -> [String] 
 switch provider 
 case .unknown:
 return attHostCodes + [arkadinMeetingsModeratorCode ,webexHostPin].flatMap$0
 case .att:
 return attHostCodes
 case .arkadinMeetings:
 return [arkadinMeetingsModeratorCode].flatMap$0
 case .webex:
 return [webexHostPin].flatMap$0
 case .zoom:
 return 
 
 

I think you've used the wrong abstraction here. I think that's the cause of all these switch statements.

Use Objects or structs

One thing I notice is that it seems like a ConferenceProvider should be an object, not an enum. If it were an object you could hold the provider's name, a link to the ConferenceNumberDirectory entry for that provider, the toll key and the toll free key. Then most of your switch statements in the first example go away, and it just becomes extracting the information from the passed-in provider. It could look something like this:

struct ConferenceProvider 
 let providerName : String
 let providerNumbers : [ConferenceNumber]
 let tollKey : String
 let tollFreeKey : String

 init(providerName: String, providerNumbers: [ConferenceNumber], tollKey: String, tollFreeKey: String) 
 self.providerName = providerName
 self.providerNumbers = providerNumbers
 self.tollKey = tollKey
 self.tollFreeKey = tollFreeKey
 

You'd then have to change getDirectory(for conferenceProvider: ) to do the lookup by name, or some other method. You'd probably want a Dictionary that mapped provider name to the above ConferenceProvider struct.