Custom Validations

You can also define custom validation logic for your fields. Let’s add a custom validation to the title field to ensure it is longer than 2 characters.

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

  @Fields.string<Task>({
    validate: (task) => task.title.length > 2 || 'too short',
  })
  title = ''

  //....
}

Code Explanation

• We added a custom validation function to the title field using the validate option.
• The custom validation function checks if the title field’s length is greater than 2. If the condition is not met, it returns the error message 'too short'.
• We specified the Task type in the generic definition of Fields.string<Task>, which provides type safety and ensures the custom validation function receives the correct type.
• This arrow function will run both on the frontend as frontend validation and on the backend as API validation, ensuring consistent validation across the stack.

Try It Out

Try adding tasks with titles shorter than 3 characters to see the custom validation in action. The error message 'too short' will be returned if the validation fails.