Tuesday, November 29, 2016

Locale-Based Message Support Added to vadacl

The latest release of my vadacl validation library for Angular 2 introduces a new feature:  locale-based error message configuration.

Prior to this release, vadacl would allow you to configure the error message for a particular validation error condition for a particular object property in either the object-based validation settings or in the component responsible for the form controls.  And if you did not declare an error message in either of those places, the validation method would return a method-specific default error message from the Messages object.  So in the following (slightly-contrived) scenario:


// app/vadacl/locale/messages-en.ts
let Messages = {
  /* DEFAULT LOCALE VALIDATOR ERROR MESSAGES */
  required: 'A value is required',
  ...
}


// app/domain/user-profile.ts
...
export class UserProfile implements Validatable {
  firstName: string = null;
  lastName: string = null;
  username: string = null;
  age: number = null;
  gender: string = null;

  validations: { [ index: string ] : PropertyValidations } = {
    firstName: {
       required: { message: 'Your first name is required.' }
    },
    lastName: {
       required: {}
    },
    username: {
       required: { message: 'Username is required.' }
    },
    age: {
       required: {}
    },
    gender: {
       required: {}
    }
  };
  ...
}

// app/forms/user-profile-form.component.ts
...
export class UserProfileForm extends Vadacl implements OnInit {
  profileForm: FormGroup;
  userProfile: UserProfile;
  ...

  ngOnInit() {
    this.userProfile = new UserProfile();

    this.profileForm = new FormGroup({
      'firstName': new FormControl(
         this.userProfile.firstName,
         this.applyRules( this.userProfile, 'firstName' )
      ),

      'lastName': new FormControl(
         this.userProfile.lastName,
         this.applyRules( this.userProfile, 'lastName', { required: { message: 'Your last name is required.' } )
      ),

      'username': new FormControl(
         this.userProfile.username,
         this.applyRules( this.userProfile, 'username', { required: { message: 'Please enter a username.' } )
      ),

      'age': new FormControl(
         this.userProfile.age,
         this.applyRules( this.userProfile, 'age' )
      ),

      'gender': new FormControl(
         this.userProfile.gender,
         this.applyRules( this.userProfile, 'gender' )
      )
    });
  }
  ...
}
...the validation error message for each UserProfile property in the UserProfileForm template that fails the required validation would be:
  • firstName: "Your first name is required."
  • lastName: "Your last name is required." (the message is provided during the FormControl instantiation)
  • username: "Please enter a username." (the component-level message overrides the object-level message)
  • age: "A value is required"
  • gender: "A value is required"

Now vadacl provides the option to configure error messages for object properties in the Messages object rather than in the validation settings in the object. Refactoring the example above to use the new feature, the code would look like:


// app/vadacl/locale/messages-en.ts
let Messages = {
  /* DEFAULT LOCALE VALIDATOR ERROR MESSAGES */
  required: 'A value is required',
  ...

  /* LOCALE-BASED DOMAIN CLASS MESSAGES */
  UserProfile: {
    firstName: {
      required: 'First name is required.'
    },
    lastName: {
      required: 'Last name is required.'
    },
    username: {
      required: 'Username is required.'
    }
  }
  ...
}

// app/domain/user-profile.ts
...
export class UserProfile implements Validatable { 
  ...
  validations: { [ index: string ] : PropertyValidations } = {
    firstName: { required: {} },
    lastName: { required: {} },
    username: { required: {} },
    age: { required: {} },
    gender: { required: {} }
  };
  ...
}

// app/forms/user-profile-form.component.ts
...
  'lastName': new FormControl(
    this.userProfile.lastName,
    this.applyRules( this.userProfile, 'lastName' )
  ),

  'username': new FormControl(
    this.userProfile.username,
    this.applyRules( this.userProfile, 'username', { required: { message: 'Please enter a username.' } )
  ),
...
...and the error messages would now be:
  • firstName: "First name is required."
  • lastName: "Last name is required."
  • username: "Please enter a username."
  • age: "A value is required"
  • gender: "A value is required"

The validation message defaults to the message in the Messages object that matches the object / property / validation method combination. If a different message is defined for that property in the object validation settings (which ordinarily you wouldn't do if you wanted to use the locale-based messages in the Messages object) or in the component when configuring the FormControl, that other message would become the message value returned when validation fails.

Configuring the validation messages in the Messages object allows you to keep all of the object-level messages in one place.  In theory, this should also give developers who need to perform internationalization the option of creating Messages objects for different languages and then altering which Messages file is imported into validation-methods.ts file as a build step prior to compiling the app.

Friday, November 11, 2016

vadacl: A Library For Streamlining Form Validation in Angular 2

The initial version of my TypeScript-based vadacl library for performing form validation in Angular 2 is now available on GitHub.

vadacl provides the following enhancements to the typical implementation of form validation via the reactive form classes (FormControl, FormGroup, FormArray, and FormBuilder):

  • Instead of configuring all of the validation in the component hosting the form, you can configure certain validations within the data object itself (validation rules that should remain consistent wherever the data object is used in your application), then add to or modify those validation rules in the component to create the final set of validations needed for a given form.

  • The vadacl validation methods add a "message" property to the metadata object returned when the form data fails validation.  This "message" property value is the message meant to be presented to the user, and can be configured and/or overridden at multiple levels:

    • The method level, via a set of default message values
    • The data object
    • The component level
  • The Vadacl class, whether used as a superclass for your component or as a service, provides methods for providing an array of validator methods to the FormControls in your form and for displaying the validation error "message" values in your template, removing the need to add multiple DOM elements with "ngIf" directives to display each kind of validation error or to add code to your component to gather and translate validation failures into error messages.

vadacl is (currently) a small library contained in a single folder you can just drop into your Angular application. The GitHub repo contains that folder as part of a small Angular 2.1.1 application containing several working demos of vadacl in action.

Enjoy!

Tuesday, November 8, 2016

Learning Angular 2: Implementing My vadacl Validation Library

Version 0.0.7 of my sandbox GuildRunner Angular 2 application is a refactor of the sandbox Chapter form I created in the previous version.  I refactored the form, which uses Angular's reactive form classes (FormControl, FormGroup, FormArray, and FormBuilder) to use a small validation library I created called vadacl.

The two main features of vadacl are:

  • It allows developers to set validation rules for the properties of a domain class at both the domain class level and the component level (because some validations are there to ensure the data can be persisted back to the server, and those validations should be set on the domain class so they are consistent throughout the application).

  • It gives developers the ability to set a "message" value that will be part of the metadata object returned from a validator when the data is invalid (which you can see in action in the refactored sandbox Chapter form).

You can read more about vadacl in my blog post about the library and in the README file in the vadacl GitHub repo.