danveloper

class LocalPaymentService implements PaymentService {
  	static {
		use (PaymentTypeHandlerRegistrationCategory) {
			CreditCardPaymentType.register(CreditCardPaymentProcessor)
			GiftCardPaymentType.register(GiftCardPaymentProcessor)
			EmployeePaymentType.register(EmployeePaymentProcessor)
			CheckPaymentType.register(CheckPaymentProcessor)
		}
	}

danveloper

class LocalPaymentService implements PaymentService {
  	static {
		use (PaymentTypeHandlerRegistrationCategory) {
			CreditCardPaymentType.register(CreditCardPaymentProcessor)
			GiftCardPaymentType.register(GiftCardPaymentProcessor)
			EmployeePaymentType.register(EmployeePaymentProcessor)
			CheckPaymentType.register(CheckPaymentProcessor)
		}
	}

danveloper

class PaymentTypeHandlerRegistrationCategory {
  	static final registry = [:]

	// type => handler registration
	static def register(Class type, Class handler) {
		registry[type] = handler
	}

	static def getHandler(Class type) {
		registry[type]

danveloper

class CheckPaymentProcessor {
  	static String process(PaymentType paymentType) {
		def gateway = new CheckPaymentProcessor()
		// … implementation code ...
	}
}

danveloper

class LocalPaymentService implements PaymentService {

  	public String process(PaymentType paymentType) {
		if (paymentType instanceof CreditCardPaymentType) {
			use (CreditCardPaymentProcessor) {
				return paymentType.process()
			}
		}
		// ...
	}

danveloper

class CreditCardPaymentProcessor {
        static {
            CreditCardPaymentProcessor.metaClass.static.methodMissing = { String name, args ->
                if (name.startsWith("getGatewayFor")) {
                    def state = name.replaceAll("getGatewayFor","")?.toLowerCase()
                    switch (state) {
                        case "ca":
                            return new CheckPaymentProcessor()
                        default:
                            return new CreditCardPaymentProcessor()

danveloper

class LocalPaymentService implements PaymentService {
  
	// Dependency injected from container
	CreditCardPaymentGateway creditCardPaymentGateway
	GiftCardPaymentGateway giftCardPaymentGateway
	CheckPaymentGateway checkPaymentGateway
	EmployeePaymentGateway employeePaymentGateway

	public String process(PaymentType paymentType) throws IllegalArgumentException {
		if (paymentType instanceof CreditCardPaymentType) {

danveloper

class LocalPaymentService implements PaymentService {
  
	// Dependency injected from container
	CreditCardPaymentGateway creditCardPaymentGateway
	GiftCardPaymentGateway giftCardPaymentGateway
	CheckPaymentGateway checkPaymentGateway
	EmployeePaymentGateway employeePaymentGateway

	public String process(PaymentType paymentType) throws IllegalArgumentException {
		if (paymentType instanceof CreditCardPaymentType) {

danveloper

class LocalPaymentService implements PaymentService {
  
	// Dependency injected from container
	CreditCardPaymentGateway creditCardPaymentGateway
	GiftCardPaymentGateway giftCardPaymentGateway
	CheckPaymentGateway checkPaymentGateway
	EmployeePaymentGateway employeePaymentGateway

	public String process(PaymentType paymentType) throws IllegalArgumentException {
		if (paymentType instanceof CreditCardPaymentType) {

danveloper

class Payee {
  	String name
	String phoneNumber
	Address billingAddress
}

public interface PaymentType {
	Payee getPayee();
}