Understanding Validation Rules and Validation Results in Aurelia

In Aurelia, validation is an essential aspect of building robust and user-friendly applications. The Aurelia Validation library provides a powerful and flexible way to validate user input. Two fundamental concepts in Aurelia Validation are validation rules and validation results. In this article, we will delve into the differences between these two concepts and explore how they work together to provide a seamless validation experience.

Validation Rules

A validation rule is a function that defines a specific validation criterion for a particular property or field in your application. It is a way to specify the conditions under which a value is considered valid or invalid. Validation rules can be simple or complex, depending on the requirements of your application.

For example, you might have a validation rule that checks if a username is at least 3 characters long, or another rule that verifies if an email address is in the correct format. Validation rules are typically defined using the `ValidationRules` class in Aurelia Validation.

import { ValidationRules } from 'aurelia-validation';

ValidationRules
  .ensure('username')
  .required()
  .minLength(3)
  .on(this);

Validation Results

A validation result, on the other hand, represents the outcome of applying a validation rule to a specific value. It indicates whether the value is valid or invalid, and if invalid, provides information about the error. Validation results are typically represented by the `ValidationResult` class in Aurelia Validation.

A validation result can have one of three possible states:

• Valid: The value is valid according to the validation rule.
• Invalid: The value is invalid according to the validation rule.
• Pending: The validation rule is still being evaluated, and the result is not yet available.

import { ValidationResult } from 'aurelia-validation';

const result = this.validator.validate();
if (result.valid) {
  console.log('The value is valid');
} else {
  console.log('The value is invalid');
}

Key Differences

The main differences between validation rules and validation results are:

• Validation rules define the validation criteria, while validation results represent the outcome of applying those criteria.
• Validation rules are typically defined once and reused throughout the application, while validation results are generated dynamically each time a value is validated.
• Validation rules are concerned with the logic of validation, while validation results are concerned with the outcome of that logic.

Conclusion

In conclusion, validation rules and validation results are two fundamental concepts in Aurelia Validation that work together to provide a seamless validation experience. Validation rules define the validation criteria, while validation results represent the outcome of applying those criteria. By understanding the differences between these two concepts, you can build more robust and user-friendly applications with Aurelia.

Frequently Asked Questions

What is the purpose of validation rules in Aurelia?

Validation rules define the validation criteria for a particular property or field in your application.

What is the purpose of validation results in Aurelia?

Validation results represent the outcome of applying a validation rule to a specific value.

How are validation rules defined in Aurelia?

Validation rules are typically defined using the `ValidationRules` class in Aurelia Validation.

How are validation results represented in Aurelia?

Validation results are typically represented by the `ValidationResult` class in Aurelia Validation.

What are the possible states of a validation result?

A validation result can have one of three possible states: Valid, Invalid, or Pending.