A Contract is an abstract class that implements the Optionable interface, which provides an options object layer, and is meant to be inherited from as a super class. All classes that extend Contract accept an options object through the constructor, which is validated and built using optimal.

To start, extend Contract with a generic interface that represents the shape of the options object. Next, implement the abstract Contract#blueprint() method, which is passed optimal predicates as an argument, and must return an optimal blueprint that matches the generic interface.

import { Contract, Blueprint, Predicates } from '@boost/common';
export interface AdapterOptions {
name?: string;
priority?: number;
export default class Adapter extends Contract<AdapterOptions> {
blueprint({ number, string }: Predicates): Blueprint<AdapterOptions> {
return {
name: string().notEmpty(),
priority: number().gte(0),

When the class is instantiated, the provided values will be checked and validated using the blueprint. If invalid, an error will be thrown. Furthermore, the Contract#options property is readonly, and will error when mutated.

const adapter = new Adapter({
name: 'Boost',
const { name } = adapter.options; // => Boost

Required options#

By default, the options argument in the constructor is optional, and if your interface has a required property, it will not be bubbled up in TypeScript. To support this, the constructor will need to be overridden so that the argument can be marked as non-optional.

export interface AdapterOptions {
name: string;
priority?: number;
export default class Adapter extends Contract<AdapterOptions> {
constructor(options: AdapterOptions) {
// ...



Contract#blueprint(predicates: Predicates, onConstruction: boolean): Blueprint<T>

Shape of the options object passed to the constructor or to Contract#configure(). Utilizes optimal for strict and thorough validation checks.

A boolean is passed as the 2nd argument to determine whether this is validating on class instantiation (first time), or by calling configure() (all other times).


Contract#configure(options?: Partial<T> | ((options: Required<T>) => Partial<T>)): Readonly<Required<T>>

Use this method to modify the options object after instantiation. This method accepts a partial object, or a function that receives the current full options object and must return a partial object.

adapter.configure({ name: 'Boost' });
adapter.configure((prevOptions) => ({
nestedObject: {
some: 'value',