ValueObject

Can be used to measure or describe things (name, description, amount, height, date, time, range, address, etc.)

ValueObjects are only identified by their values, (for example money is a value object as long as we are not tracking individual banknotes, if we need to track individual banknotes then it should be a banknote entity)

Basically, they are all the attributes you need to validate the status and they don't have a unique ID

import { Result, ValueObject } from 'types-ddd';

interface Prop {
  value: string;
}

class EmailValueObject extends ValueObject<Prop> {
  private constructor(prop: Prop) {
    super(prop);
  }

  get value(): string {
    return this.props.value;
  }

  public static isValidEmail (email: string): boolean {
    const regex = /^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$/g;
    return regex.test(email);
  }
  
  public static create(value: string): Result<EmailValueObject> {
    
    const isValid = EmailValueObject.isValidEmail(value);
    
    if (!isValid) {
      return Result.fail<EmailValueObject>('Invalid email');
    }
    
    return Result.ok<EmailValueObject>(
      new EmailValueObject({ value: value.toLowerCase() }),
    );
    
  }
}

Lets test our ValueObject

const emailOrError = EmailValueObject.create("[e-mail]");

console.log(emailOrError);
> Result: {
  "isSuccess": true,
  "isFailure": false,
  "error": null,
  "statusCode": "OK",
  "statusCodeNumber": 200,
  "_value": {
    "props": {
      "value": "[e-mail]"
    }
  }
} 

Now lets see a fail example

const emailOrError = EmailValueObject.create("invalid_email");

console.log(emailOrError);
> Result: {
  "isSuccess": false,
  "isFailure": true,
  "error": "Invalid email",
  "_value": null,
  "statusCodeNumber": 422,
  "statusCode": "UNPROCESSABLE_ENTITY"
} 

How to get the ValueObject value

You always have to validate if the result is a failure before getting the result

emailOrError.isFailure;

> false

const emailOrError = EmailValueObject.create("[e-mail]");

const emailValueObject = emailOrError.getResult();

console.log(emailValueObject.value);

> "[e-mail]"