danveloper

class Student {
    enum DormHall {
        Honors, Preferred, Normal
    }
    def firstName
    def lastName
    def gpa
    
    // We only want dormHall to be assigned when it is deliberate, so throw an exception when
    // it is accidentally assigned outside of our rules engine

danveloper

class RulesEngineSupport<E> {
    RulesEngine engine
    E obj
    
    // Deduce the rule list for a given RulesEngine instance
    def getRules() {
        def rules = []
        engine.class.declaredFields.each {
            def field = engine."${it.name}"
            if (!it.isSynthetic() && field instanceof Closure && it.name.endsWith("Rule")) {

danveloper

class RulesEngineFactory<E extends RulesEngine> {
    private final E engine
    public RulesEngineFactory(final Class<E> c) {
        this.engine = (E)c.newInstance()
        this.engine.engine = this.engine
    }
    
    def getObject(final def obj) {
        this.engine.obj = obj
        this.engine

danveloper

public interface RulesEngine {}

danveloper

class EnrollmentProcessor {
    static def enrollmentRulesFactory = new RulesEngineFactory<EnrollmentRulesEngine>(EnrollmentRulesEngine)
    def studentService
    
    def annualDormHallAssignment() {
        def students = Student.list(/* do some filtering maybe to make sure they are enrolling for this year,etc. */)
        def errors = []
        students.each { student ->
            try {
                def studentEnrollmentRulesEngine = enrollmentRulesFactory.getObject(student)

danveloper

/**
*
*   Structure:
*    + module: model
*      - class: com.danveloper.model.Student
*
**/
class Student {
    enum DormHall {
        Honors, Preferred, Normal

danveloper

public enum PaymentVendor {
    INTERNAL, STRIPE;
}

public class ProductOrder {
    Account account;
    Address shippingAddress;
    PaymentMethod paymentMethod;
    double taxRate = 0.0;
    PaymentVendor paymentVendor = PaymentVendor.STRIPE;

danveloper

public class Account {
    String email;
    int orderCount;
}

danveloper

public class Address {
    Object street, unit, city, state, zip;
}

danveloper

public interface PaymentMethod {
    enum PaymentMethodType {
        GIFT_CARD, CREDIT_CARD
    }

    PaymentMethodType getType();
}

public class GiftCard implements PaymentMethod {
    String number;