validator-inator

    //This is used so that you can pass dependencies to validation functions
    //e.g. if you want to call a web service you could reference it here
    type MyValidationContext = {};

    const registry = new ValidationRegistry<MyValidationContext>();

    const AddressType = t.type({
        ID: t.number,
        StreetAddress1: t.string,
        City: t.string,
        State: t.string
    });

    class Address extends tdc.DeriveClass(AddressType) {}

    const PersonType = t.type({
        ID: t.number,
        FirstName: t.string,
        LastName: t.string,
        Email: t.union([t.string, t.null]),
        Phone: t.union([t.string, t.null]),
        Addresses: t.array(tdc.ref(Address))
    });

    class Person extends tdc.DeriveClass(PersonType) {}

    const mustHaveContactMethodValidator = (p: Person) => {
        const validResult = { Email: null, Phone: null, Addresses: null };
        if (p.Email !== null || p.Phone !== null || p.Addresses.length > 0) {
            return validResult;
        }

        const message =
        "A person must have an Email or a Phone or a Physical Address!";

        return { Email: message, Phone: message, Addresses: message };
    };

    registry.register(Person, {
        FirstName: required(),
        LastName: [required(), min(1)],
        Email: mustHaveContactMethodValidator,
        Phone: mustHaveContactMethodValidator,
        Addresses: mustHaveContactMethodValidator
    });

    let testPerson = new Person()
    let validationResult = await registry.validate(testPerson, {})