DomainError

Overview

The domain error component helps you better organize the errors associated with the domain of your application by providing an understandable and easily modified template. This way your errors are well documented and identifiable by both the developers and users of your application.

Syntax

 DomainError InvalidName(name: string) {
   message: `${name} is an invalid name`,
   errorId: 'e5a0bd82-8ef7-4b1a-ab67-cb83d1d7772fe',
 }

As you might have observed the command mainly consists of 2 fields the message and the errorId. The errorId is the unique identifier of your domain errors and it helps you better identify them in your application.

The message property is were you get specific on what your error actually mean. This part will most likely be the one that is displayed to the people interacting with your application and it is where good definition actually plays a big role. Luckily the bitloops language utilizes typeScript's template string mechanism that enables the injection of variables in your message string. You can use the arguments that are passed in your object to dynamically define your errors based on circumstances.

As you can observe in the example above we can utilize this mechanic and be more specific about the name that caused the error.

Usage Example

ValueObject Name {
  const regName = /^[a-zA-Z ]{2,30}$/;

  isInvalidName(name: string): bool {
    return !regName.test(name);
  }

  create(props: NameProps): (OK(Name), Error(DomainErrors.InvalidName)) {
    if (isInvalidName(props.name)) {
      return new DomainErrors.InvalidName(props.name);
    } else {
      return new Name(props);
    }
  }
}

DomainError InvalidName(name: string) {
  message: `${name} is an invalid name`,
  errorId: 'e5a0bd82-8ef7-4b1a-ab67-cb83d1d7772fe',
}

As you can see in the example above the validity of the name is something that is related with your domain and it is therefore a meaningful error. It is therefore defined inside the Name entity and it is returned at the appropriate case of the create method.