Aurelia Validation: Validating User Input with aurelia-validation

Aurelia-validation is a popular validation library for Aurelia applications. It provides a simple and intuitive way to validate user input, ensuring that the data entered by users meets the required criteria. In this article, we will explore how to use aurelia-validation to validate user input in Aurelia.

Setting up aurelia-validation

To use aurelia-validation, you need to install the aurelia-validation package using npm or yarn:

npm install aurelia-validation

or

yarn add aurelia-validation

Once installed, you need to configure aurelia-validation in your Aurelia application. You can do this by adding the following code to your main.js file:

import { Validation } from 'aurelia-validation';

export function configure(aurelia) {
  aurelia.use
    .standardConfiguration()
    .developmentLogging()
    .plugin('aurelia-validation');

  aurelia.start().then(() => aurelia.setRoot());
}

Creating a Validation Rule

A validation rule is a function that takes a value as input and returns a boolean indicating whether the value is valid or not. You can create a validation rule using the ValidationRule class:

import { ValidationRule } from 'aurelia-validation';

export class EmailRule extends ValidationRule {
  validate(value) {
    const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
    return emailRegex.test(value);
  }
}

In this example, the EmailRule class extends the ValidationRule class and overrides the validate method. The validate method takes a value as input and returns a boolean indicating whether the value is a valid email address or not.

Validating a Form

To validate a form, you need to create a validation controller and add validation rules to it. You can create a validation controller using the ValidationController class:

import { ValidationController } from 'aurelia-validation';

export class MyForm {
  constructor(private validationController: ValidationController) {}

  async validate() {
    const result = await this.validationController.validate();
    if (result.valid) {
      // form is valid
    } else {
      // form is not valid
    }
  }
}

In this example, the MyForm class has a validationController property that is injected by Aurelia. The validate method is called to validate the form. If the form is valid, the result.valid property is true. Otherwise, it is false.

Adding Validation Rules to a Form

To add validation rules to a form, you need to use the validate method of the validation controller. You can pass an array of validation rules to the validate method:

import { ValidationController } from 'aurelia-validation';
import { EmailRule } from './email-rule';

export class MyForm {
  constructor(private validationController: ValidationController) {}

  async validate() {
    const rules = [
      new EmailRule('email', 'Email address is not valid'),
    ];

    const result = await this.validationController.validate(rules);
    if (result.valid) {
      // form is valid
    } else {
      // form is not valid
    }
  }
}

In this example, the validate method is called with an array of validation rules. The EmailRule class is used to validate the email address.

Displaying Validation Errors

To display validation errors, you can use the validation-errors attribute on a div element:

<div validation-errors.bind="validationController.errors"></div>

This will display a list of validation errors for the form.

Conclusion

In this article, we have explored how to use aurelia-validation to validate user input in Aurelia. We have seen how to create a validation rule, validate a form, add validation rules to a form, and display validation errors. aurelia-validation is a powerful library that makes it easy to validate user input in Aurelia applications.

FAQs

What is aurelia-validation?

aurelia-validation is a validation library for Aurelia applications.

How do I install aurelia-validation?

You can install aurelia-validation using npm or yarn.

How do I create a validation rule?

You can create a validation rule by extending the ValidationRule class and overriding the validate method.

How do I validate a form?

You can validate a form by creating a validation controller and adding validation rules to it.

How do I display validation errors?

You can display validation errors by using the validation-errors attribute on a div element.