Form.ts

type Input<A> = { title: string; value: A };

type Form<A> = { [P in keyof A]: Input<A[P]> };

//An example model
type Person = {
  firstName: string;
  lastName: string;
  children: number;
};

//all properties of the Person type must be supplied
//the value must be of the defined type
const form: Form<Person> = {
  firstName: {
    title: "First Name",
    value: "Reid"
  },
  lastName: {
    title: "Last Name",
    value: "Evans"
  },
  children: {
    title: "Number of Children",
    value: 3
  }
};

FormStates.ts

type FormState<T> = { values: T } & (
  | { status: "unsubmitted"; validationFailures: { [K in keyof T]: string } }
  | { status: "processing"; message: string }
  | { status: "errored"; errors: { [K in keyof T]: string }; message: string }
  | { status: "complete"; message: string });