AUR4203

Error Message

AUR4203: {{controller}} is not of type ValidationController

Description

This error occurs when the validate binding behavior receives an object that is not a proper ValidationController instance. This typically happens when:

1. The validation controller is not properly injected

2. A different object is mistakenly passed as the controller

3. The controller instance is null or undefined

Common Scenarios

// ❌ Problem: Invalid controller type
export class MyComponent {
  controller = {}; // Not a ValidationController
}

Solution

// ✅ Correct: Proper validation controller injection
import { ValidationController, ValidationControllerFactory } from '@aurelia/validation-html';

export class MyComponent {
  validationController: ValidationController;
  
  constructor(controllerFactory: ValidationControllerFactory) {
    this.validationController = controllerFactory.createForCurrentScope();
  }
}