Validator

The Validator<TModel> generic class is the core component of the fluentvalidation-ts API.

import { Validator } from 'fluentvalidation-ts';

To define a validator for a model of type TModel all you have to do is define a class which extends Validator<TModel> and specify some rules in the constructor using the .ruleFor and .ruleForEach methods.

type FormModel = { name: string };

class FormValidator extends Validator<FormModel> {
  constructor() {
    super();

    this.ruleFor('name')
      .notEmpty()
      .withMessage('Please enter your name');
  }
}

To actually validate an instance of your model, simply create an instance of your validator and pass your model to the .validate method.

const formValidator = new FormValidator();

const validResult = formValidator.validate({ name: 'Alex' });
// ✔ {}

const invalidResult = formValidator.validate({ name: '' });
// ❌ { name: 'Please enter your name' }

A call to .validate returns an object of type ValidationErrors<TModel>, which describes the validity of the given value.