The Foundation for Proper Form Management in Angular

🔮 Features

✅ Allows Typed Forms! ✅ Auto persists the form's state upon user navigation. ✅ Provides an API to reactively querying any form, from anywhere. ✅ Persist the form's state to local storage. ✅ Built-in dirty functionality.

NgFormsManager lets you sync Angular’s FormGroup, FormControl, and FormArray, via a unique store created for that purpose. The store will hold the controls' data like values, validity, pristine status, errors, etc.

This is powerful, as it gives you the following abilities:

1. It will automatically save the current control value and update the form value according to the value in the store when the user navigates back to the form.
2. It provides an API so you can query a form’s values and properties from anywhere. This can be useful for things like multi-step forms, cross-component validation and more.
3. It can persist the form's state to local storage.

The goal in creating this was to work with the existing Angular form ecosystem, and save you the trouble of learning a new API. Let’s see how it works:

First, install the library:

Installation

npm i @ngneat/forms-manager

Then, create a component with a form:

import { NgFormsManager } from '@ngneat/forms-manager';

@Component({
  template: `
    <form [formGroup]="onboardingForm">
      <input formControlName="name" />
      <input formControlName="age" />
      <input formControlName="city" />
    </form>
  `,
})
export class OnboardingComponent {
  onboardingForm: FormGroup;

  constructor(private formsManager: NgFormsManager, private builder: FormBuilder) {}

  ngOnInit() {
    this.onboardingForm = this.builder.group({
      name: [null, Validators.required],
      age: [null, Validators.required],
      city: [null, Validators.required],
    });

    this.formsManager.upsert('onboarding', this.onboardingForm);
  }

  ngOnDestroy() {
    this.formsManager.unsubscribe('onboarding');
  }
}

As you can see, we’re still working with the existing API in order to create a form in Angular. We’re injecting the NgFormsManager and calling the upsert method, giving it the form name and an AbstractForm. From that point on, NgFormsManager will track the form value changes, and update the store accordingly.

With this setup, you’ll have an extensive API to query the store and update the form from anywhere in your application:

API

• valueChanges() - Observe the control's value

const value$ = formsManager.valueChanges('onboarding');
const nameValue$ = formsManager.valueChanges<string>('onboarding', 'name');

• validityChanges() - Whether the control is valid

const valid$ = formsManager.validityChanges('onboarding');
const nameValid$ = formsManager.validityChanges('onboarding', 'name');

• dirtyChanges() - Whether the control is dirty

const dirty$ = formsManager.dirtyChanges('onboarding');
const nameDirty$ = formsManager.dirtyChanges('onboarding', 'name');

• disableChanges() - Whether the control is disabled

const disabled$ = formsManager.disableChanges('onboarding');
const nameDisabled$ = formsManager.disableChanges('onboarding', 'name');

• errorsChanges() - Observe the control's errors

const errors$ = formsManager.errorsChanges<Errors>('onboarding');
const nameErrors$ = formsManager.errorsChanges<Errors>('onboarding', 'name');

• controlChanges() - Observe the control's state

const control$ = formsManager.controlChanges('onboarding');
const nameControl$ = formsManager.controlChanges<string>('onboarding', 'name');

• getControl() - Get the control's state

const control = formsManager.getControl('onboarding');
const nameControl = formsManager.getControl<string>('onboarding', 'name');

controlChanges and getControl will return the following state:

{
   value: any,
   rawValue: object,
   errors: object,
   valid: boolean,
   dirty: boolean,
   invalid: boolean,
   disabled: boolean,
   touched: boolean,
   pristine: boolean,
   pending: boolean,
   untouched: boolean,
}

• hasControl() - Whether the control exists

const hasControl = formsManager.hasControl('onboarding');

• patchValue() - A proxy to the original patchValue method

formsManager.patchValue('onboarding', value, options);

• setValue() - A proxy to the original setValue method

formsManager.setValue('onboarding', value, options);

• reset() - A proxy to the original reset method

formsManager.reset('onboarding', value, options);

• markAllAsTouched() - A proxy to the original markAllAsTouched method

formsManager.markAllAsTouched('onboarding', options);

• markAsTouched() - A proxy to the original markAsTouched method

formsManager.markAsTouched('onboarding', options);

• markAllAsDirty() - Marks the control and all its descendant controls as dirty

formsManager.markAllAsDirty('onboarding', options);

• markAsDirty() - A proxy to the original markAsDirty method

formsManager.markAsDirty('onboarding', options);

• markAsPending() - A proxy to the original markAsPending method

formsManager.markAsPending('onboarding', options);

• markAsPristine() - A proxy to the original markAsPristine method

formsManager.markAsPristine('onboarding', options);

• markAsUntouched() - A proxy to the original markAsUntouched method

formsManager.markAsUntouched('onboarding', options);

• unsubscribe() - Unsubscribe from the form's valueChanges observable (always call it on ngOnDestroy)

formsManager.unsubscribe('onboarding');
formsManager.unsubscribe();

• clear() - Delete the form from the store

formsManager.clear('onboarding');
formsManager.clear();

• destroy() - Destroy the form (Internally calls clear and unsubscribe)

formsManager.destroy('onboarding');
formsManager.destroy();

• controlDestroyed() - Emits when the control is destroyed

formsManager.controlChanges('login').pipe(takeUntil(controlDestroyed('login')));

Persist to browser storage (localStorage, sessionStorage or custom storage solution)

In the upsert method, pass the persistState flag:

formsManager.upsert(formName, abstractContorl, {
  persistState: true,
});

By default, the state is persisted to localStorage (Link).

For storage to sessionStorage (Link), add FORMS_MANAGER_SESSION_STORAGE_PROVIDER to the providers array in app.module.ts:

import { FORMS_MANAGER_SESSION_STORAGE_PROVIDER } from '@ngneat/forms-manager';

@NgModule({
  declarations: [AppComponent],
  imports: [ ... ],
  providers: [
    ...
    FORMS_MANAGER_SESSION_STORAGE_PROVIDER,
    ...
  ],
  bootstrap: [AppComponent],
})
export class AppModule {}

Furthermore, a custom storage provider, which must implement the Storage interface (Link) can be provided through the FORMS_MANAGER_STORAGE token:

import { FORMS_MANAGER_STORAGE } from '@ngneat/forms-manager';

class MyStorage implements Storage {
  public clear() { ... }
  public key(index: number): string | null { ... }
  public getItem(key: string): string | null { ... }
  public removeItem(key: string) { ... }
  public setItem(key: string, value: string) { ... }
}

@NgModule({
  declarations: [AppComponent],
  imports: [ ... ],
  providers: [
    ...
    {
      provide: FORMS_MANAGER_STORAGE,
      useValue: MyStorage,
    },
    ...
  ],
  bootstrap: [AppComponent],
})
export class AppModule {}

Validators

The library exposes two helpers method for adding cross component validation:

export function setValidators(
  control: AbstractControl,
  validator: ValidatorFn | ValidatorFn[] | null
);

export function setAsyncValidators(
  control: AbstractControl,
  validator: AsyncValidatorFn | AsyncValidatorFn[] | null
);

Here's an example of how we can use it:

export class HomeComponent{
  ngOnInit() {
    this.form = new FormGroup({
      price: new FormControl(null, Validators.min(10))
    });

    /*
    * Observe the `minPrice` value in the `settings` form
    * and update the price `control` validators
    */
    this.formsManager.valueChanges<number>('settings', 'minPrice')
     .subscribe(minPrice => setValidators(this.form.get('price'), Validators.min(minPrice));
  }
}

Using FormArray Controls

When working with a FormArray, it's required to pass a factory function that defines how to create the controls inside the FormArray. For example:

import { NgFormsManager } from '@ngneat/forms-manager';

export class HomeComponent {
  skills: FormArray;
  config: FormGroup;

  constructor(private formsManager: NgFormsManager<FormsState>) {}

  ngOnInit() {
    this.skills = new FormArray([]);

    /** Or inside a FormGroup */
    this.config = new FormGroup({
      skills: new FormArray([]),
    });

    this.formsManager
      .upsert('skills', this.skills, { arrControlFactory: value => new FormControl(value) })
      .upsert('config', this.config, {
        arrControlFactory: { skills: value => new FormControl(value) },
      });
  }

  ngOnDestroy() {
    this.formsManager.unsubscribe();
  }
}

NgFormsManager Generic Type

NgFormsManager can take a generic type where you can define the forms shape. For example:

interface AppForms {
  onboarding: {
    name: string;
    age: number;
    city: string;
  };
}

This will make sure that the queries are typed, and you don't make any mistakes in the form name.

export class OnboardingComponent {
  constructor(private formsManager: NgFormsManager<AppForms>, private builder: FormBuilder) {}

  ngOnInit() {
    this.formsManager.valueChanges('onboarding').subscribe(value => {
      // value now typed as AppForms['onboarding']
    });
  }
}

Note that you can split the types across files using a definition file:

// login-form.d.ts
interface AppForms {
  login: {
    email: string;
    password: string
  }
}

// onboarding.d.ts
interface AppForms {
  onboarding: {
    ...
  }
}

Using the Dirty Functionality

The library provides built-in support for the common "Is the form dirty?" question. Dirty means that the current control's value is different from the initial value. It can be useful when we need to toggle the visibility of a "save" button or displaying a dialog when the user leaves the page.

To start using it, you should set the withInitialValue option:

@Component({
  template: `
    <button *ngIf="isDirty$ | async">Save</button>
  `,
})
export class SettingsComponent {
  isDirty$ = this.formsManager.initialValueChanged(name);

  constructor(private formsManager: NgFormsManager<AppForms>) {}

  ngOnInit() {
    this.formsManager.upsert(name, control, {
      withInitialValue: true,
    });
  }
}

setInitialValue(name, value) - Set the initial form's value

formsManager.setInitialValue('form', initialValue);

getInitialValue(name) - Get the initial value or undefined if not exist.

formsManager.getInitialValue('form');

NgFormsManager Config

You can override the default config by passing the NG_FORMS_MANAGER_CONFIG provider:

import { NG_FORMS_MANAGER_CONFIG, NgFormsManagerConfig } from '@ngneat/forms-manager';

@NgModule({
  declarations: [AppComponent],
  imports: [ReactiveFormsModule],
  providers: [
    {
      provide: NG_FORMS_MANAGER_CONFIG,
      useValue: new NgFormsManagerConfig({
        debounceTime: 1000, // defaults to 300
        storage: {
          key: 'NgFormManager',
        },
      }),
    },
  ],
  bootstrap: [AppComponent],
})
export class AppModule {}

Contributors ✨

Thanks goes to these wonderful people (emoji key):

This project follows the all-contributors specification. Contributions of any kind welcome!