Objective-C binding in Xamarin.Forms

Question

Simulator Exception:

System.Exception: Could not create an native instance of the type 'TPBinding.Worldpay': the native class hasn't been loaded.

Device Exception:

ObjCRuntime.RuntimeException: Wrapper type 'TPBinding.Worldpay' is missing its native ObjectiveC class 'Worldpay'.

I have created a binding for the following Objective C lib for use in an Xmarin.Forms application via Dependency Service

https://github.com/Worldpay/worldpay-lib-ios

I have created the CocoaPods Static lib to generate and combine the necessary binaries and ultimately the fat lib for use within the Binding project. Running the following lipo & nm commands leads me to think I'm good up to this point.

Development:Products ***$ lipo -info libWorldpayStaticAll
Architectures in the fat file: libWorldpayStaticAll are: armv7 armv7s i386 x86_64 arm64 

Development:Products ***$ nm libWorldpayStaticAll

I have successfully generated the ApiDefinitions & Structs&Enums for the binding project below

using System;
using Foundation;
using ObjCRuntime;
using PassKit;
using UIKit;

namespace TPBinding
{
    // @interface APMController : UIViewController
    [BaseType(typeof(UIViewController))]
    [Protocol]
    interface APMController
    {
        // @property (nonatomic) UIView * customToolbar;
        [Export("customToolbar", ArgumentSemantic.Assign)]
        UIView CustomToolbar { get; set; }

        // @property (nonatomic) float price;
        [Export("price")]
        float Price { get; set; }

        // @property (retain, nonatomic) NSString * apmName;
        [Export("apmName", ArgumentSemantic.Retain)]
        string ApmName { get; set; }

        // @property (retain, nonatomic) NSString * customerOrderCode;
        [Export("customerOrderCode", ArgumentSemantic.Retain)]
        string CustomerOrderCode { get; set; }

        // @property (retain, nonatomic) NSString * orderDescription;
        [Export("orderDescription", ArgumentSemantic.Retain)]
        string OrderDescription { get; set; }

        // @property (retain, nonatomic) NSDictionary * customerIdentifiers;
        [Export("customerIdentifiers", ArgumentSemantic.Retain)]
        NSDictionary CustomerIdentifiers { get; set; }

        // @property (retain, nonatomic) NSString * successUrl;
        [Export("successUrl", ArgumentSemantic.Retain)]
        string SuccessUrl { get; set; }

        // @property (retain, nonatomic) NSString * failureUrl;
        [Export("failureUrl", ArgumentSemantic.Retain)]
        string FailureUrl { get; set; }

        // @property (retain, nonatomic) NSString * cancelUrl;
        [Export("cancelUrl", ArgumentSemantic.Retain)]
        string CancelUrl { get; set; }

        // @property (retain, nonatomic) NSString * pendingUrl;
        [Export("pendingUrl", ArgumentSemantic.Retain)]
        string PendingUrl { get; set; }

        // @property (retain, nonatomic) NSString * address;
        [Export("address", ArgumentSemantic.Retain)]
        string Address { get; set; }

        // @property (retain, nonatomic) NSString * city;
        [Export("city", ArgumentSemantic.Retain)]
        string City { get; set; }

        // @property (retain, nonatomic) NSString * postalCode;
        [Export("postalCode", ArgumentSemantic.Retain)]
        string PostalCode { get; set; }

        // @property (retain, nonatomic) NSString * token;
        [Export("token", ArgumentSemantic.Retain)]
        string Token { get; set; }

        // @property (retain, nonatomic) NSString * name;
        [Export("name", ArgumentSemantic.Retain)]
        string Name { get; set; }

        // @property (retain, nonatomic) NSString * currencyCode;
        [Export("currencyCode", ArgumentSemantic.Retain)]
        string CurrencyCode { get; set; }

        // @property (retain, nonatomic) NSString * settlementCurrency;
        [Export("settlementCurrency", ArgumentSemantic.Retain)]
        string SettlementCurrency { get; set; }

        // @property (retain, nonatomic) NSString * countryCode;
        [Export("countryCode", ArgumentSemantic.Retain)]
        string CountryCode { get; set; }

        // -(void)setAuthorizeAPMOrderBlockWithSuccess:(authorizeAPMOrderSuccess)success failure:(authorizeAPMOrderFailure)failure;
        [Export("setAuthorizeAPMOrderBlockWithSuccess:failure:")]
        void SetAuthorizeAPMOrderBlockWithSuccess(authorizeAPMOrderSuccess success, authorizeAPMOrderFailure failure);
    }

    // typedef void (^authorizeAPMOrderSuccess)(NSDictionary *);
    delegate void authorizeAPMOrderSuccess(NSDictionary arg0);

    // typedef void (^authorizeAPMOrderFailure)(NSDictionary *, NSArray *);
    delegate void authorizeAPMOrderFailure(NSDictionary arg0, NSObject[] arg1);

    // @interface ThreeDSController : UIViewController
    [BaseType(typeof(UIViewController))]
    [Protocol]
    interface ThreeDSController
    {
        // @property (nonatomic) UIView * customToolbar;
        [Export("customToolbar", ArgumentSemantic.Assign)]
        UIView CustomToolbar { get; set; }

        // @property (nonatomic) float price;
        [Export("price")]
        float Price { get; set; }

        // @property (retain, nonatomic) NSString * address;
        [Export("address", ArgumentSemantic.Retain)]
        string Address { get; set; }

        // @property (retain, nonatomic) NSString * city;
        [Export("city", ArgumentSemantic.Retain)]
        string City { get; set; }

        // @property (retain, nonatomic) NSString * postalCode;
        [Export("postalCode", ArgumentSemantic.Retain)]
        string PostalCode { get; set; }

        // @property (retain, nonatomic) NSString * token;
        [Export("token", ArgumentSemantic.Retain)]
        string Token { get; set; }

        // @property (retain, nonatomic) NSString * name;
        [Export("name", ArgumentSemantic.Retain)]
        string Name { get; set; }

        // @property (nonatomic) NSDictionary * customerIdentifiers;
        [Export("customerIdentifiers", ArgumentSemantic.Assign)]
        NSDictionary CustomerIdentifiers { get; set; }

        // -(void)setAuthorizeThreeDSOrderBlockWithSuccess:(threeDSOrderSuccess)success failure:(threeDSOrderFailure)failure;
        [Export("setAuthorizeThreeDSOrderBlockWithSuccess:failure:")]
        void SetAuthorizeThreeDSOrderBlockWithSuccess(threeDSOrderSuccess success, threeDSOrderFailure failure);
    }

    // typedef void (^threeDSOrderSuccess)(NSDictionary *);
    delegate void threeDSOrderSuccess(NSDictionary arg0);

    // typedef void (^threeDSOrderFailure)(NSDictionary *, NSArray *);
    delegate void threeDSOrderFailure(NSDictionary arg0, NSObject[] arg1);

    // @interface Worldpay : NSObject
    [BaseType(typeof(NSObject))]
    [Protocol]
    interface Worldpay
    {
        // @property (nonatomic) WorldpayValidationType validationType;
        [Export("validationType", ArgumentSemantic.Assign)]
        WorldpayValidationType ValidationType { get; set; }

        // @property (retain, nonatomic) NSString * clientKey;
        [Export("clientKey", ArgumentSemantic.Retain)]
        string ClientKey { get; set; }

        // @property (retain, nonatomic) NSString * serviceKey;
        [Export("serviceKey", ArgumentSemantic.Retain)]
        string ServiceKey { get; set; }

        // @property (nonatomic) BOOL reusable;
        [Export("reusable")]
        bool Reusable { get; set; }

        // @property (nonatomic) BOOL authorizeOnly;
        [Export("authorizeOnly")]
        bool AuthorizeOnly { get; set; }

        // @property (retain, nonatomic) NSString * tokenType;
        [Export("tokenType", ArgumentSemantic.Retain)]
        string TokenType { get; set; }

        // +(Worldpay *)sharedInstance;
        [Static]
        [Export("sharedInstance")]
        //[Verify(MethodToProperty)]
        Worldpay SharedInstance();

        // -(NSString *)APIStringURL;
        [Export("APIStringURL")]
        //[Verify(MethodToProperty)]
        string APIStringURL { get; }

        // -(void)createTokenWithNameOnCard:(NSString *)holderName cardNumber:(NSString *)cardNumber expirationMonth:(NSString *)expirationMonth expirationYear:(NSString *)expirationYear CVC:(NSString *)CVC success:(requestUpdateTokenSuccess)success failure:(requestTokenFailure)failure;
        [Export("createTokenWithNameOnCard:cardNumber:expirationMonth:expirationYear:CVC:success:failure:")]
        void CreateTokenWithNameOnCard(string holderName, string cardNumber, string expirationMonth, string expirationYear, string CVC, requestUpdateTokenSuccess success, requestTokenFailure failure);

        // -(void)createAPMTokenWithAPMName:(NSString *)apmName countryCode:(NSString *)countryCode apmFields:(NSDictionary *)apmFields shopperLanguageCode:(NSString *)shopperLanguageCode success:(requestUpdateTokenSuccess)success failure:(requestTokenFailure)failure;
        [Export("createAPMTokenWithAPMName:countryCode:apmFields:shopperLanguageCode:success:failure:")]
        void CreateAPMTokenWithAPMName(string apmName, string countryCode, NSDictionary apmFields, string shopperLanguageCode, requestUpdateTokenSuccess success, requestTokenFailure failure);

        // -(void)reuseToken:(NSString *)token withCVC:(NSString *)CVC success:(requestUpdateTokenSuccess)success failure:(updateTokenFailure)failure;
        [Export("reuseToken:withCVC:success:failure:")]
        void ReuseToken(string token, string CVC, requestUpdateTokenSuccess success, updateTokenFailure failure);

        // -(void)showCVCModalWithParentView:(UIView *)parentView token:(NSString *)token success:(requestUpdateTokenSuccess)success error:(updateTokenFailure)failure __attribute__((deprecated("")));
        [Export("showCVCModalWithParentView:token:success:error:")]
        void ShowCVCModalWithParentView(UIView parentView, string token, requestUpdateTokenSuccess success, updateTokenFailure failure);

        // -(void)showCVCModalWithParentView:(UIView *)parentView token:(NSString *)token success:(requestUpdateTokenSuccess)success beforeRequest:(void (^)(void))beforeRequest error:(updateTokenFailure)failure;
        [Export("showCVCModalWithParentView:token:success:beforeRequest:error:")]
        void ShowCVCModalWithParentView(UIView parentView, string token, requestUpdateTokenSuccess success, Action beforeRequest, updateTokenFailure failure);

        // -(NSString *)stripCardNumberWithCardNumber:(NSString *)cardNumber;
        [Export("stripCardNumberWithCardNumber:")]
        string StripCardNumberWithCardNumber(string cardNumber);

        // -(BOOL)validateCardNumberBasicWithCardNumber:(NSString *)cardNumber;
        [Export("validateCardNumberBasicWithCardNumber:")]
        bool ValidateCardNumberBasicWithCardNumber(string cardNumber);

        // -(BOOL)validateCardNumberAdvancedWithCardNumber:(NSString *)cardNumber;
        [Export("validateCardNumberAdvancedWithCardNumber:")]
        bool ValidateCardNumberAdvancedWithCardNumber(string cardNumber);

        // -(BOOL)validateCardExpiryWithMonth:(int)month year:(int)year;
        [Export("validateCardExpiryWithMonth:year:")]
        bool ValidateCardExpiryWithMonth(int month, int year);

        // -(BOOL)validateCardCVCWithNumber:(NSString *)cvc;
        [Export("validateCardCVCWithNumber:")]
        bool ValidateCardCVCWithNumber(string cvc);

        // -(BOOL)validateCardHolderNameWithName:(NSString *)holderName;
        [Export("validateCardHolderNameWithName:")]
        bool ValidateCardHolderNameWithName(string holderName);

        // -(NSArray *)validateCardDetailsWithCVC:(NSString *)CVC token:(NSString *)token;
        [Export("validateCardDetailsWithCVC:token:")]
        //[Verify(StronglyTypedNSArray)]
        NSArray ValidateCardDetailsWithCVC(string CVC, string token);

        // -(NSArray *)validateCardDetailsWithHolderName:(NSString *)holderName cardNumber:(NSString *)cardNumber expirationMonth:(NSString *)expirationMonth expirationYear:(NSString *)expirationYear CVC:(NSString *)CVC;
        [Export("validateCardDetailsWithHolderName:cardNumber:expirationMonth:expirationYear:CVC:")]
        //[Verify(StronglyTypedNSArray)]
        NSArray ValidateCardDetailsWithHolderName(string holderName, string cardNumber, string expirationMonth, string expirationYear, string CVC);

        // -(NSArray *)validateAPMDetailsWithAPMName:(NSString *)apmName countryCode:(NSString *)countryCode;
        [Export("validateAPMDetailsWithAPMName:countryCode:")]
        //[Verify(StronglyTypedNSArray)]
        NSArray ValidateAPMDetailsWithAPMName(string apmName, string countryCode);

        // -(BOOL)validateAPMNameWithName:(NSString *)apmName;
        [Export("validateAPMNameWithName:")]
        bool ValidateAPMNameWithName(string apmName);

        // -(BOOL)validateCountryCodeWithCode:(NSString *)countryCode;
        [Export("validateCountryCodeWithCode:")]
        bool ValidateCountryCodeWithCode(string countryCode);

        // -(NSString *)cardType:(NSString *)cardNumber;
        [Export("cardType:")]
        string CardType(string cardNumber);

        // -(NSError *)errorWithTitle:(NSString *)title code:(NSInteger)code;
        [Export("errorWithTitle:code:")]
        NSError ErrorWithTitle(string title, nint code);

        // -(void)makeRequestWithURL:(NSString *)url requestDictionary:(NSDictionary *)requestDictionary method:(NSString *)method success:(requestUpdateTokenSuccess)success failure:(requestTokenFailure)failure additionalHeaders:(NSDictionary *)additionalHeaders;
        [Export("makeRequestWithURL:requestDictionary:method:success:failure:additionalHeaders:")]
        void MakeRequestWithURL(string url, NSDictionary requestDictionary, string method, requestUpdateTokenSuccess success, requestTokenFailure failure, NSDictionary additionalHeaders);
    }

    // typedef void (^requestUpdateTokenSuccess)(int, NSDictionary *);
    delegate void requestUpdateTokenSuccess(int arg0, NSDictionary arg1);

    // typedef void (^requestTokenFailure)(NSDictionary *, NSArray *);
    delegate void requestTokenFailure(NSDictionary arg0, NSObject[] arg1);

    // typedef void (^updateTokenFailure)(NSDictionary *, NSArray *);
    delegate void updateTokenFailure(NSDictionary arg0, NSObject[] arg1);

    // @interface ApplePay (Worldpay)
    [Category]
    [BaseType(typeof(Worldpay))]
    interface Worldpay_ApplePay
    {
        // -(BOOL)canMakePayments;
        [Export("canMakePayments")]
        // [Verify(MethodToProperty)]
        bool CanMakePayments();

        // -(PKPaymentRequest *)createPaymentRequestWithMerchantIdentifier:(NSString *)marchantIdentifier;
        [Export("createPaymentRequestWithMerchantIdentifier:")]
        PKPaymentRequest CreatePaymentRequestWithMerchantIdentifier(string marchantIdentifier);

        // -(void)createTokenWithPayment:(PKPayment *)payment success:(requestUpdateTokenSuccess)success failure:(requestTokenFailure)failure;
        [Export("createTokenWithPayment:success:failure:")]
        void CreateTokenWithPayment(PKPayment payment, requestUpdateTokenSuccess success, requestTokenFailure failure);

        // -(void)createTokenWithPaymentData:(NSData *)paymentData success:(requestUpdateTokenSuccess)success failure:(requestTokenFailure)failure;
        [Export("createTokenWithPaymentData:success:failure:")]
        void CreateTokenWithPaymentData(NSData paymentData, requestUpdateTokenSuccess success, requestTokenFailure failure);
    }

    // @interface WorldpayAPMViewController : UIViewController <UITextFieldDelegate>
    [BaseType(typeof(UIViewController))]
    [Protocol]
    interface WorldpayAPMViewController : IUITextFieldDelegate
    {
        // @property (nonatomic) UIToolbar * customToolbar;
        [Export("customToolbar", ArgumentSemantic.Assign)]
        UIToolbar CustomToolbar { get; set; }

        // @property (nonatomic) UIButton * confirmPurchaseButton;
        [Export("confirmPurchaseButton", ArgumentSemantic.Assign)]
        UIButton ConfirmPurchaseButton { get; set; }

        // @property (nonatomic) NSString * apmName;
        [Export("apmName")]
        string ApmName { get; set; }

        // @property (nonatomic) NSString * address;
        [Export("address")]
        string Address { get; set; }

        // @property (nonatomic) NSString * city;
        [Export("city")]
        string City { get; set; }

        // @property (nonatomic) NSString * postcode;
        [Export("postcode")]
        string Postcode { get; set; }

        // @property (nonatomic) NSString * name;
        [Export("name")]
        string Name { get; set; }

        // @property (nonatomic) NSString * countryCode;
        [Export("countryCode")]
        string CountryCode { get; set; }

        // @property (nonatomic) NSString * currency;
        [Export("currency")]
        string Currency { get; set; }

        // @property (nonatomic) NSString * settlementCurrency;
        [Export("settlementCurrency")]
        string SettlementCurrency { get; set; }

        // @property (nonatomic) NSString * successUrl;
        [Export("successUrl")]
        string SuccessUrl { get; set; }

        // @property (nonatomic) NSString * cancelUrl;
        [Export("cancelUrl")]
        string CancelUrl { get; set; }

        // @property (nonatomic) NSString * failureUrl;
        [Export("failureUrl")]
        string FailureUrl { get; set; }

        // @property (nonatomic) NSString * pendingUrl;
        [Export("pendingUrl")]
        string PendingUrl { get; set; }

        // @property (nonatomic) NSString * shopperLanguageCode;
        [Export("shopperLanguageCode")]
        string ShopperLanguageCode { get; set; }

        // @property (nonatomic) NSString * swiftCode;
        [Export("swiftCode")]
        string SwiftCode { get; set; }

        // @property (nonatomic) NSString * customerOrderCode;
        [Export("customerOrderCode")]
        string CustomerOrderCode { get; set; }

        // @property (nonatomic) NSString * orderDescription;
        [Export("orderDescription")]
        string OrderDescription { get; set; }

        // @property (nonatomic) NSDictionary * customerIdentifiers;
        [Export("customerIdentifiers", ArgumentSemantic.Assign)]
        NSDictionary CustomerIdentifiers { get; set; }

        // @property (nonatomic) float price;
        [Export("price")]
        float Price { get; set; }

        // @property (nonatomic) APMDetailsTheme theme;
        [Export("theme", ArgumentSemantic.Assign)]
        APMDetailsTheme Theme { get; set; }

        // @property (nonatomic) APMDetailsLoadingTheme loadingTheme;
        [Export("loadingTheme", ArgumentSemantic.Assign)]
        APMDetailsLoadingTheme LoadingTheme { get; set; }

        // -(id)initWithAPMName:(NSString *)apmName;
        [Export("initWithAPMName:")]
        IntPtr Constructor(string apmName);

        // -(id)initWithColor:(UIColor *)color loadingTheme:(APMDetailsLoadingTheme)loadingTheme apmName:(NSString *)apmName;
        [Export("initWithColor:loadingTheme:apmName:")]
        IntPtr Constructor(UIColor color, APMDetailsLoadingTheme loadingTheme, string apmName);

        // -(void)addLoadingBackground;
        [Export("addLoadingBackground")]
        void AddLoadingBackground();

        // -(void)removeLoadingBackground;
        [Export("removeLoadingBackground")]
        void RemoveLoadingBackground();

        // -(void)setCreateAPMOrderBlockWithSuccess:(createAPMOrderSuccess)success failure:(createAPMOrderFailure)failure;
        [Export("setCreateAPMOrderBlockWithSuccess:failure:")]
        void SetCreateAPMOrderBlockWithSuccess(createAPMOrderSuccess success, createAPMOrderFailure failure);
    }

    // typedef void (^createAPMOrderSuccess)(NSDictionary *);
    delegate void createAPMOrderSuccess(NSDictionary arg0);

    // typedef void (^createAPMOrderFailure)(NSDictionary *, NSArray *);
    delegate void createAPMOrderFailure(NSDictionary arg0, NSObject[] arg1);

    // @interface WorldpayCardViewController : UIViewController <UITextFieldDelegate>
    [BaseType(typeof(UIViewController))]
    [Protocol]
    interface WorldpayCardViewController : IUITextFieldDelegate
    {
        // @property (nonatomic) CardDetailsTheme theme;
        [Export("theme", ArgumentSemantic.Assign)]
        CardDetailsTheme Theme { get; set; }

        // @property (nonatomic) CardDetailsLoadingTheme loadingTheme;
        [Export("loadingTheme", ArgumentSemantic.Assign)]
        CardDetailsLoadingTheme LoadingTheme { get; set; }

        // @property (nonatomic) CardDetailsTextField textField;
        [Export("textField", ArgumentSemantic.Assign)]
        CardDetailsTextField TextField { get; set; }

        // -(id)initWithColor:(UIColor *)color loadingTheme:(CardDetailsLoadingTheme)loadingTheme;
        [Export("initWithColor:loadingTheme:")]
        IntPtr Constructor(UIColor color, CardDetailsLoadingTheme loadingTheme);

        // -(void)shakeTextField:(CardDetailsTextField)textField;
        [Export("shakeTextField:")]
        void ShakeTextField(CardDetailsTextField textField);

        // -(void)showWarningView;
        [Export("showWarningView")]
        void ShowWarningView();

        // -(void)addLoadingBackground;
        [Export("addLoadingBackground")]
        void AddLoadingBackground();

        // -(void)removeLoadingBackground;
        [Export("removeLoadingBackground")]
        void RemoveLoadingBackground();

        // -(void)setSaveButtonTapBlockWithSuccess:(requestTokenSuccess)success failure:(requestTokenFailure)failure;
        [Export("setSaveButtonTapBlockWithSuccess:failure:")]
        void SetSaveButtonTapBlockWithSuccess(requestTokenSuccess success, requestTokenFailure failure);
    }

    // typedef void (^requestTokenSuccess)(NSDictionary *);
    delegate void requestTokenSuccess(NSDictionary arg0);

    // typedef void (^requestTokenFailure)(NSDictionary *, NSArray *);
    //delegate void requestTokenFailure(NSDictionary arg0, NSObject[] arg1);

    // @interface WorldpayUtils : NSObject
    [BaseType(typeof(NSObject))]
    [Protocol]
    interface WorldpayUtils
    {
        // +(void)loadFont:(NSString *)fontName;
        [Static]
        [Export("loadFont:")]
        void LoadFont(string fontName);

        // +(void)sendDebug:(NSString *)string;
        [Static]
        [Export("sendDebug:")]
        void SendDebug(string @string);
    }
}

Simply trying to instantiate a Worldpay instance results in the following exceptions (different on Simulator & Device)

Simulator:-

System.Exception: Could not create an native instance of the type 'TPBinding.Worldpay': the native class hasn't been loaded.
It is possible to ignore this condition by setting ObjCRuntime.Class.ThrowOnInitFailure to false.
  at Foundation.NSObject.InitializeObject (System.Boolean alloced) [0x0002e] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/Foundation/NSObject2.cs:196
  at Foundation.NSObject..ctor (Foundation.NSObjectFlag x) [0x0000d] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/Foundation/NSObject2.cs:131
  at TPBinding.Worldpay..ctor () [0x00000] in /Users/davidp/Documents/TPWorldpay/WorldpayTest/TPBindings/obj/Debug/ios/TPBinding/Worldpay.g.cs:615
  at WorldpayTest.iOS.Services.NativePaymentService.Init () [0x00001] in /Users/davidp/Documents/TPWorldpay/WorldpayTest/WorldpayTest.iOS/Services/NativePaymentService.cs:13
  at WorldpayTest.Views.ItemsPage.OnAppearing () [0x00008] in /Users/davidp/Documents/TPWorldpay/WorldpayTest/WorldpayTest/Views/ItemsPage.xaml.cs:51
  at Xamarin.Forms.Page.SendAppearing () [0x00024] in D:\a\1\s\Xamarin.Forms.Core\Page.cs:359
  at Xamarin.Forms.Platform.iOS.PageRenderer.ViewDidAppear (System.Boolean animated) [0x0004b] in <6d6f830f76b442a8953f9ae13539c687>:0
  at at (wrapper managed-to-native) 

Physical Device:-

ObjCRuntime.RuntimeException: Wrapper type 'TPBinding.Worldpay' is missing its native ObjectiveC class 'Worldpay'.
  at Registrar.DynamicRegistrar.OnRegisterType (Registrar.Registrar+ObjCType type) [0x000e1] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/DynamicRegistrar.cs:847
  at Registrar.Registrar.RegisterTypeUnsafe (System.Type type, System.Collections.Generic.List`1[System.Exception]& exceptions) [0x00f05] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/Registrar.cs:2369
  at Registrar.Registrar.RegisterType (System.Type type, System.Collections.Generic.List`1[System.Exception]& exceptions) [0x00011] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/Registrar.cs:1441
  at Registrar.DynamicRegistrar.Register (System.Type type) [0x00002] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/DynamicRegistrar.cs:1163
  at ObjCRuntime.Class.Register (System.Type type) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/Class.cs:237
  at ObjCRuntime.Class.GetClassHandle (System.Type type, System.Boolean throw_if_failure, System.Boolean& is_custom_type) [0x000ea] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/Class.cs:170
  at ObjCRuntime.Class.GetClassHandle (System.Type type) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/Class.cs:181
  at ObjCRuntime.Class.GetHandle (System.Type type) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/ObjCRuntime/Class.cs:134
  at Foundation.NSObject.AllocIfNeeded () [0x00012] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/Foundation/NSObject2.cs:511
  at Foundation.NSObject..ctor (Foundation.NSObjectFlag x) [0x00006] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/Foundation/NSObject2.cs:130
  at TPBinding.Worldpay..ctor () [0x00000] in /Users/davidp/Documents/TPWorldpay/WorldpayTest/TPBindings/obj/Debug/ios/TPBinding/Worldpay.g.cs:615
  at WorldpayTest.iOS.Services.NativePaymentService.Init () [0x00001] in /Users/davidp/Documents/TPWorldpay/WorldpayTest/WorldpayTest.iOS/Services/NativePaymentService.cs:13
  at WorldpayTest.Views.ItemsPage.OnAppearing () [0x00008] in /Users/davidp/Documents/TPWorldpay/WorldpayTest/WorldpayTest/Views/ItemsPage.xaml.cs:51
  at Xamarin.Forms.Page.SendAppearing () [0x00024] in D:\a\1\s\Xamarin.Forms.Core\Page.cs:359
  at Xamarin.Forms.Platform.iOS.PageRenderer.ViewDidAppear (System.Boolean animated) [0x0004b] in <6d6f830f76b442a8953f9ae13539c687>:0
  at at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/UIKit/UIApplication.cs:86

I have been looking at the linking side of things but I am usure as to where I go now?