RxFormMapper is a framework developed for angular and allows you to convert, by annotation, classes into reactive form and vice versa.

What is RxFormMapper

Reactive forms use an explicit and immutable approach to managing the state of a form at a given point in time. Each change to the form state returns a new state, which maintains the integrity of the model between changes. Reactive forms are built around observable streams, where form inputs and values are provided as streams of input values, which can be accessed synchronously.

So... Why RxFormMapper?

Sometimes you want to transform the classes you have into reactive forms, for example you have a user model that you want to have filled out by a form:

export class User {
	name: string;
	surname: string;
	age: number;
}

So what to do? How to make a user form ? Solution is to create new instances of Reactive Form object and manually copy all properties to new object. But things may go wrong very fast once you have a more complex object hierarchy.

new FormGroup(
	name: new FormControl(user.name),
	surname: new FormControl(user.surname),
	age: new FormControl(user.age),
);

To avoid all this you can use RxFormMapper:

export class User {

	@FormControl()
	name: string;

	@FormControl()
	surname: string;

	@FormControl()
	age: number;
}

import { Component } from '@angular/core';
import { FormControl } from '@angular/forms';
import { User } from 'src/app/models/user.model';

@Component({
	selector: 'app-user-editor',
	templateUrl: './user-editor.component.html',
	styleUrls: ['./user-editor.component.css']
})
export class UserEditorComponent {

	public form: FormGroup;
	constructor(rxFormMapper: RxFormMapper) {
		this.form = rxFormMapper.writeForm(User);
	}
}

Try it

See it in action at https://stackblitz.com/edit/rx-form-mapper-example?file=src/app/user-registration.ts

Getting started

Install npm package

npm i rx-form-mapper --save

reflect-metadata is required (with angular+ you should already have this dependency installed.)

npm i reflect-metadata --save

Import the component modules

Import the NgModule for RxFormMapper

import { RxFormMapperModule } from 'rx-form-mapper';

@NgModule({
  ...
  imports: [RxFormMapperModule.forRoot()],
  ...
})
export class MyAppModule { }

Inject RxFormMapper in your component

import { RxFormMapper } from 'rx-form-mapper';

@Component({ ... })
export class MyComponent { 
	constructor(private readonly rxFormMapper: RxFormMapper) {}
}

Build your form

import { RxFormMapper } from 'rx-form-mapper';
import { Component } from '@angular/core';
import { FormGroup } from '@angular/forms';
import { User } from 'src/app/models/user.model';

@Component({ ... })
export class MyComponent { 
	public myForm: FormGroup;
	constructor(rxFormMapper: RxFormMapper) {
		this.myForm = rxFormMapper.writeForm(new User());
	}
}

Modules

RxFormMapperModule

This module enables RxFormMapper features

Services

RxFormMapper

This service provides the methods to serialize and deserialize our objects

Methods

writeForm

This method converts our class instance into reactive form instance

this.form = formMapper.writeForm(new Post());

fromType

This method converts our class type into reactive form instance

this.form = formMapper.fromType(Post);

readForm

This method converts our form instance into specific class instance

const post: Post = formMapper.readForm(this.form, Post);

Decorators

@FormControl

If you want to expose some of properties as a FormControl, you can do it by @FormControl decorator

import { FormControl } from 'rx-form-mapper';

export class User {

	@FormControl()
	name: string;

	@FormControl()
	surname: string;

	@FormControl()
	age: number;
}

@FormGroup

If you want to expose some of properties as a FormGroup, you can do it by @FormGroup decorator

import { FormGroup } from 'rx-form-mapper';

export class Child {}

export class User {
	@FormGroup()
	child: Child;
}

@FormArray

If you want to expose some of properties as a FormArray, you can do it by @FormArray decorator

import { FormGroup } from 'rx-form-mapper';

export class Child {}

export class User {
	@FormArray(Child)
	children: Child[];
}

When you're trying to serialize a property into FormArray its required to known what type of object you are trying to convert.

@Form

If you want to add extra data to your form, you can do it by optional @Form decorator

import { Form } from 'rx-form-mapper';

@Form({
	validators: Validators.required
})
export class User {

	@FormControl()
	name: string;

	@FormControl()
	surname: string;

	@FormControl()
	age: number;
}

@CustomControl

If you want to create custom forms for specific fields, you can do it by @CustomControl decorator

Declare your custom mapper class implementing CustomControlMapper interface

import { CustomControlMapper } from 'rx-form-mapper';
import { AbstractControlOptions, FormControl } from '@angular/forms';

export class CustomAuthorControlMapper implements CustomControlMapper {

	public writeForm(value: any, abstractControlOptions: AbstractControlOptions): AbstractControl {
		return new FormControl(value, abstractControlOptions);
	}

	public readForm(control: AbstractControl): ChildTestClass {
		return control.value;
	}

}

And pass it's type as argument of CustomControl decorator

import { Form } from 'rx-form-mapper';
import { CustomAuthorControlMapper } from '.';

export class Post {

	@CustomControl(CustomAuthorControlMapper)
	author: Person;

}

Injectable CustomMapper

Sometimes you want to injects other services into your CustomMapper, RxFormMapper allows you to do it simple:

Declare your CustomControlMapper class, decorate with @Injectable and includes it in a module as a normal service.

import { CustomControlMapper } from 'rx-form-mapper';
import { AbstractControlOptions, FormControl } from '@angular/forms';

@Injectable()
export class CustomAuthorControlMapper implements CustomControlMapper {

	public writeForm(value: any, abstractControlOptions: AbstractControlOptions): AbstractControl {
		return new FormControl(value, abstractControlOptions);
	}

	public readForm(control: AbstractControl): ChildTestClass {
		return control.value;
	}

}

And pass it's type as validator or asyncValidator option

import { Form } from 'rx-form-mapper';
import { CustomAuthorControlMapper } from '.';

export class Post {

	@CustomControl(CustomAuthorControlMapper)
	author: Person;

}

Validators

If you want to set a validator on a class or a property, you can do it by specifying validators option to @Form, @FormControl,@CustomControl or @FormArray decorators

import { FormControl } from 'rx-form-mapper';

export class User {

	@FormControl({
		validators: Validators.required
	})
	completeName: string;

}

Async validators

If you want to set an AsyncValidator on a class or a property, you can do it by specifying asyncValidators option to @Form, @FormControl,@CustomControl or @FormArray decorators

import { FormControl } from 'rx-form-mapper';

const asyncValidator = (control: AbstractControl) => return of(undefined);

export class User {


	@FormControl({
		asyncValidators: asyncValidator
	})
	name: string;

}

Injectable validators

Sometimes you want to injects other services into your validator or asyncValidator, RxFormMapper allows you to do it simple with Angular Forms interfaces:

Declare your validator class implementing Validator or AsyncValidator interfaces, decorate with @Injectable and includes it in a module as a normal service.

import { AsyncValidator } from '@angular/forms';

@Injectable()
export class UniqueNameValidator implements AsyncValidator {

	constructor(private readonly http: HttpProvider) {}

	public validate(control: AbstractControl): Promise<ValidationErrors> | Observable<ValidationErrors> {
		// implementation
	}

}

And pass it's type as validator or asyncValidator option

import { FormControl } from 'rx-form-mapper';
import { UniqueNameValidator } from 'src/app/validators/unique-Name.validator';

export class User {

	@FormControl({
		asyncValidators: UniqueNameValidator
	})
	name: string;

}

Validation strategy

Sometimes you want to change the default strategy of form validation, you can do it specifying updateOn option to @Form, @FormControl,@CustomControl or @FormArray decorators

import { FormControl } from 'rx-form-mapper';

export class User {

	@FormControl({
		validators: Validators.required,
		updateOn: 'blur'
	})
	name: string;

}