Built-In Validations

Remult comes with a set of built-in validations that you can easily choose from. These validations are defined in the Validators class.

Minimum Length Validation

For example, let’s use the minLength validation:

export class Task {
  @Fields.uuid()
  id = ''

  @Fields.string<Task>({
    validate: Validators.minLength(2),
  })
  title = ''

  //....
}

Code Explanation

• We added the validate option to the title field using the Validators.minLength(2) validation.
• This ensures that the title field must have at least 2 characters.

Chaining Multiple Validators

You can also chain multiple validators:

export class Task {
  @Fields.uuid()
  id = ''

  @Fields.string<Task>({
    validate: [Validators.minLength(2), Validators.maxLength(5)],
  })
  title = ''

  //....
}

Code Explanation

• We chained the Validators.minLength(2) and Validators.maxLength(5) validations.
• This ensures that the title field must have at least 2 characters and at most 5 characters.

Customizing Validation Messages

You can also customize the validation message:

export class Task {
  @Fields.uuid()
  id = ''

  @Fields.string<Task>({
    validate: [
      Validators.minLength(2),
      Validators.maxLength(5, (length) => `maximum ${length} characters`),
    ],
  })
  title = ''

  //....
}

Code Explanation

• We customized the validation message for the Validators.maxLength(5) validation.
• The custom message function (length) => 'maximum ${length} characters' will be used if the validation fails.

Try It Out

Try adding tasks with titles that do not meet these validation requirements to see the validation in action. The errors returned will include the validation messages specified.