How can a form inside a child component extend an existing form passed in by a parent component?
Desired effect: if one of the child forms is invalid, the parent form should become invalid as well.
I am using reactive forms. The number of child components can vary.
export class AddressFormComponent implements OnInit {
#Input() addressesForm; // This is the parent form
#Input() addressData;
addressForm;
constructor(private formBuilder: FormBuilder) {}
ngOnInit() {
this.addressForm = this.formBuilder.group({
...
});
// Trying to add this to the parent form will break the application (Maximum call stack size exceeded)
this.addressesForm.push(this.addressesForm);
}
I have made a simplified plunker: https://plnkr.co/edit/GymI5CqSACFEvhhz55l1?p=preview.
Related
Let's say I have two child components A and B
A has a button that should add a value to a grid select box column and B has the grid which has a vue select box for a column using
cellRenderer: 'tag-grid-select',
I want to be able to click on the button in A to refresh the select component in the grid in component B.
Note: This is not parent to child communication but child to child specifically using the Vue3 composition api and setup().
I was able to solve this using an eventbus. With this you can communicate with any component regardless of the relationship. I use npm package mitt
Here is some code I used for child to child communication
Component A -- contains ag-grid-vue
export default {
setup() {
return {
gridApi: null,
gridColumnApi: null,
}
},
async mounted() {
this.eventBus.on('refreshGrid', (args) => {
this.refreshGrid(args)
})
}
methods:
{
refreshGrid(params) {
this.gridApi.redrawRows()
},
async onGridReady(params) {
this.gridApi = params.api;
this.gridColumnApi = params.columnApi;
}
}
Component B - function that emits the command to be received by Component A
this.eventBus.emit('refreshGrid', {yourdata})
You will need to import and setup mitt according to their docs. I added it to my main.js so I did not have to import it in any page.
import mitt from 'mitt'
const eventBus = mitt()
app.config.globalProperties.eventBus = eventBus
Is there some chance to simple update _viewContainer??
I am trying create directive for material-button component, that add hidden classic button for submit form by hit enter key. I need to add simple html to _viewContainer, something like this
import 'package:angular/angular.dart';
#Directive(
selector: '[kpMaterialSubmit]',
)
class KpMaterialSubmit {
final TemplateRef _templateRef;
final ViewContainerRef _viewContainer;
KpMaterialSubmit(this._viewContainer, this._templateRef);
#Input()
set kpMaterialSubmit(bool showButton) {
_viewContainer.clear();
if (showButton) {
_viewContainer.createEmbeddedView(_templateRef);
//THIS IS THE IMPORTANT PART
_viewContainer.createMyCustomView('<button class="hidden">Submit</button>');
} else {
_viewContainer.createEmbeddedView(_templateRef);
}
}
}
I have done something similar and it works. I don't know if there is a better way.
Instead of using html text directly, create a component.
Add the import to the component template:
import 'package:<your package>/<path to component>/<component source name>.template.dart';
Then add the component with the createComponent() method (instead of createMyCustomView()):
_viewContainer.createComponent(<componentName>NgFactory);
That's all!
If you need to style the component or add any attribute you can get the reference and derive the HtmlElement instance:
ComponentRef _componentRef = _viewContainer.createComponent(<componentName>NgFactory);
HtmlElement element = _componentRef.location;
element.style.background = 'green';
element.setAttribute('value', 'text');
I'm trying to create a custom form control in Angular (v5). The custom control is essentially a wrapper around an Angular Material component, but with some extra stuff going on.
I've read various tutorials on implementing ControlValueAccessor, but I can't find anything that accounts for writing a component to wrap an existing component.
Ideally, I want a custom component that displays the Angular Material component (with some extra bindings and stuff going on), but to be able to pass in validation from the parent form (e.g. required) and have the Angular Material components handle that.
Example:
Outer component, containing a form and using custom component
<form [formGroup]="myForm">
<div formArrayName="things">
<div *ngFor="let thing of things; let i = index;">
<app-my-custom-control [formControlName]="i"></app-my-custom-control>
</div>
</div>
</form>
Custom component template
Essentially my custom form component just wraps an Angular Material drop-down with autocomplete. I could do this without creating a custom component, but it seems to make sense to do it this way as all the code for handling filtering etc. can live within that component class, rather than being in the container class (which doesn't need to care about the implementation of this).
<mat-form-field>
<input matInput placeholder="Thing" aria-label="Thing" [matAutocomplete]="thingInput">
<mat-autocomplete #thingInput="matAutocomplete">
<mat-option *ngFor="let option of filteredOptions | async" [value]="option">
{{ option }}
</mat-option>
</mat-autocomplete>
</mat-form-field>
So, on the input changing, that value should be used as the form value.
Things I've tried
I've tried a few ways of doing this, all with their own pitfalls:
Simple event binding
Bind to keyup and blur events on the input, and then notify the parent of the change (i.e. call the function that Angular passes into registerOnChange as part of implementing ControlValueAccessor).
That sort of works, but on selecting a value from the dropdown it seems the change events don't fire and you end up in an inconsistent state.
It also doesn't account for validation (e.g. if it's "required", when a value isn;t set the form control will correctly be invalid, but the Angular Material component won't show as such).
Nested form
This is a bit closer. I've created a new form within the custom component class, which has a single control. In the component template, I pass in that form control to the Angular Material component. In the class, I subscribe to valueChanges of that and then propagate the changes back to the parent (via the function passed into registerOnChange).
This sort of works, but feels messy and like there should be a better way.
It also means that any validation applied to my custom form control (by the container component) is ignored, as I've created a new "inner form" that lacks the original validation.
Don't use ControlValueAccessor at all, and instead just pass in the form
As the title says... I tried not doing this the "proper" way, and instead added a binding to the parent form. I then create a form control within the custom component as part of that parent form.
This works for handling value updates, and to an extent validation (but it has to be created as part of the component, not the parent form), but this just feels wrong.
Summary
What's the proper way of handling this? It feels like I'm just stumbling through different anti-patterns, but I can't find anything in the docs to suggest that this is even supported.
Edit:
I've added a helper for doing just this an angular utilities library I've started: s-ng-utils. Using that you can extend WrappedFormControlSuperclass and write:
#Component({
selector: 'my-wrapper',
template: '<input [formControl]="formControl">',
providers: [provideValueAccessor(MyWrapper)],
})
export class MyWrapper extends WrappedFormControlSuperclass<string> {
// ...
}
See some more documentation here.
One solution is to get the #ViewChild() corresponding to the inner form components ControlValueAccessor, and delegating to it in your own component. For example:
#Component({
selector: 'my-wrapper',
template: '<input ngDefaultControl>',
providers: [
{
provide: NG_VALUE_ACCESSOR,
useExisting: forwardRef(() => NumberInputComponent),
multi: true,
},
],
})
export class MyWrapper implements ControlValueAccessor {
#ViewChild(DefaultValueAccessor) private valueAccessor: DefaultValueAccessor;
writeValue(obj: any) {
this.valueAccessor.writeValue(obj);
}
registerOnChange(fn: any) {
this.valueAccessor.registerOnChange(fn);
}
registerOnTouched(fn: any) {
this.valueAccessor.registerOnTouched(fn);
}
setDisabledState(isDisabled: boolean) {
this.valueAccessor.setDisabledState(isDisabled);
}
}
The ngDefaultControl in the template above is to manually trigger angular to attach its normal DefaultValueAccessor to the input. This happens automatically if you use <input ngModel>, but we don't want the ngModel here, just the value accessor. You'll need to change DefaultValueAccessor above to whatever the value accessor is for the material dropdown - I'm not familiar with Material myself.
I'm a bit late to the party but here is what I did with wrapping a component which might accept formControlName, formControl, or ngModel
#Component({
selector: 'app-input',
template: '<input [formControl]="control">',
styleUrls: ['./app-input.component.scss']
})
export class AppInputComponent implements OnInit, ControlValueAccessor {
constructor(#Optional() #Self() public ngControl: NgControl) {
if (this.ngControl != null) {
// Setting the value accessor directly (instead of using the providers) to avoid running into a circular import.
this.ngControl.valueAccessor = this;
}
}
control: FormControl;
// These are just to make Angular happy. Not needed since the control is passed to the child input
writeValue(obj: any): void { }
registerOnChange(fn: (_: any) => void): void { }
registerOnTouched(fn: any): void { }
ngOnInit() {
if (this.ngControl instanceof FormControlName) {
const formGroupDirective = this.ngControl.formDirective as FormGroupDirective;
if (formGroupDirective) {
this.control = formGroupDirective.form.controls[this.ngControl.name] as FormControl;
}
} else if (this.ngControl instanceof FormControlDirective) {
this.control = this.ngControl.control;
} else if (this.ngControl instanceof NgModel) {
this.control = this.ngControl.control;
this.control.valueChanges.subscribe(x => this.ngControl.viewToModelUpdate(this.control.value));
} else if (!this.ngControl) {
this.control = new FormControl();
}
}
}
Obviously, don't forget to unsubscribe from this.control.valueChanges
I have actually been wrapping my head around this for a while and I figured out a good solution that is very similar (or the same) as Eric's.
The thing he forgot to account for, is that you can't use the #ViewChild valueAccessor until the view has actually loaded (See #ViewChild docs)
Here is the solution: (I am giving you my example which is wrapping a core angular select directive with NgModel, since you are using a custom formControl, you will need to target that formControl's valueAccessor class)
#Component({
selector: 'my-country-select',
templateUrl: './country-select.component.html',
styleUrls: ['./country-select.component.scss'],
providers: [{
provide: NG_VALUE_ACCESSOR,
useExisting: CountrySelectComponent,
multi: true
}]
})
export class CountrySelectComponent implements ControlValueAccessor, OnInit, AfterViewInit, OnChanges {
#ViewChild(SelectControlValueAccessor) private valueAccessor: SelectControlValueAccessor;
private country: number;
private formControlChanged: any;
private formControlTouched: any;
public ngAfterViewInit(): void {
this.valueAccessor.registerOnChange(this.formControlChanged);
this.valueAccessor.registerOnTouched(this.formControlTouched);
}
public registerOnChange(fn: any): void {
this.formControlChanged = fn;
}
public registerOnTouched(fn: any): void {
this.formControlTouched = fn;
}
public writeValue(newCountryId: number): void {
this.country = newCountryId;
}
public setDisabledState(isDisabled: boolean): void {
this.valueAccessor.setDisabledState(isDisabled);
}
}
NgForm is providing an easy way to manage your forms without injecting any data in a HTML form. Input data must be injected at the component level not in a classic html tag.
<form #myForm="ngForm" (ngSubmit)="onSubmit(myForm)>...</form>
Other way is to create a form component where all the data model is binded using ngModel ;)
In Angular 2 template driven forms, I can write
<form #form="ngForm">
[...]
</form>
ngForm is a FormGroup, as fare as I could understand. How do I grab that object in the corresponding component?
class FormComponent {
formGroup: FormGroup; // How do I have the form INJECTED AUTOMATICALLY by the framework? Something like a ViewChild, but it's not a view
}
It must be simple but the documentation only shows how to use the form in the template.
Thanks
EDIT: the type of what I want to grab is NgForm, not FormGroup!
You can access any template variable from the component using ViewChild decorator. In you case:
class FormComponent {
#ViewChild('form') formGroup;
ngOnInit() {
this.formGroup.statusChanges().subscribe(() => {
// Your code here!
});
console.log(this.formGroup); // Inspect the object for other available property and methods.
}
}
How do you handle Angular 2 forms in unidirectional data flow? Especially with validation between several parent/child components?
I am using ngrx/store and model driven forms with form builder.. Is it possible to do something similar like form reducer in React and make it as a part of Store?
Do you have some articles about it?
I have created a library called ngrx-forms that does exactly what you want. You can get it on npm via:
npm install ngrx-forms --save
I recommend checking out the full README on the github page, but below you can find some examples of what you need to do to get the library up and running once installed.
Import the module:
import { StoreModule } from '#ngrx/store';
import { NgrxFormsModule } from 'ngrx-forms';
import { reducers } from './reducer';
#NgModule({
declarations: [
AppComponent,
],
imports: [
NgrxFormsModule,
StoreModule.forRoot(reducers),
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
Add a group state somewhere in your state tree via createFormGroupState and call the formGroupReducer inside your reducer:
import { Action } from '#ngrx/store';
import { FormGroupState, createFormGroupState, formGroupReducer } from 'ngrx-forms';
export interface MyFormValue {
someTextInput: string;
someCheckbox: boolean;
nested: {
someNumber: number;
};
}
const FORM_ID = 'some globally unique string';
const initialFormState = createFormGroupState<MyFormValue>(FORM_ID, {
someTextInput: '',
someCheckbox: false,
nested: {
someNumber: 0,
},
});
export interface AppState {
someOtherField: string;
myForm: FormGroupState<MyFormValue>;
}
const initialState: AppState = {
someOtherField: '',
myForm: initialFormState,
};
export function appReducer(state = initialState, action: Action): AppState {
const myForm = formGroupReducer(state.myForm, action);
if (myForm !== state.myForm) {
state = { ...state, myForm };
}
switch (action.type) {
case 'some action type':
// modify state
return state;
default: {
return state;
}
}
}
Expose the form state inside your component:
import { Component } from '#angular/core';
import { Store } from '#ngrx/store';
import { FormGroupState } from 'ngrx-forms';
import { Observable } from 'rxjs/Observable';
import { MyFormValue } from './reducer';
#Component({
selector: 'my-component',
templateUrl: './my-component.html',
})
export class MyComponent {
formState$: Observable<FormGroupState<MyFormValue>>;
constructor(private store: Store<AppState>) {
this.formState$ = store.select(s => s.myForm);
}
}
Set the control states in your template:
<form novalidate [ngrxFormState]="(formState$ | async)">
<input type="text"
[ngrxFormControlState]="(formState$ | async).controls.someTextInput">
<input type="checkbox"
[ngrxFormControlState]="(formState$ | async).controls.someCheckbox">
<input type="number"
[ngrxFormControlState]="(formState$ | async).controls.nested.controls.someNumber">
</form>
This is a fairly old question, but I couldn't find a great solution in my own quest for working with ngrx + reactive forms in Angular. As a result, I'll post my research here with hope that it may help someone else. My solution can be broken down into two parts, and I pray you (oh weathered soul) find it applicable to your problem:
1) Monitor the form element/s (for example, "keyup" event for a typical text input), and update the State from that event. This strategy comes straight out of the book search component in the ngrx example app. We can now successfully populate the State as our form changes. Awesome! 50% done!
2) The angular reactive forms guide demonstrates creating the form group in the constructor. I have seen some other people do it inside ngOnInit, but this is too late in the lifecycle for our needs (I tried, I failed). Now that we have our form group established, setup ngOnChanges to capture any changes pushed from the state, and then update the form group using patchValue. For example:
ngOnChanges(changes: SimpleChanges) {
if (changes.valueICareAbout1) {
this.myForm.patchValue({
valueICareAbout1: changes.valueICareAbout1.currentValue
});
}
if (changes.valueICareAbout2) {
this.myForm.patchValue({
valueICareAbout2: changes.valueICareAbout2.currentValue
});
}
}
In the applications I built with Angular 2, the following guideline seemed to work well:
Parent components pass data down to children via data binding. Child components request data changes by emitting output events to parent components. It is the parent components responsibility to act accordingly.
In a hierarchical component structure, data changes are handled by the lowest component that depends on the data. If there's another component higher up or a sibling that depends on the same data item, pass changes up by emitting events and leave the handling to a higher component.
This scheme works well because, for any data that is relevant to more than one component, there is a single component responsible for performing changes. Changes bubble down automatically. Components are reusable, and changes in the component tree can be easily adapted.
With regard to validation, any component in the ladder between the lowest component emitting a data change request up to the highest component that finally handles the change, any component can effectively cancel the change by not passing it higher up. In most applications, I'd opt for validating data changes at the origin of the change though.
Naturally, child components can still have internal state and need not communicate changes - unless changes are relevant to the parent component.
Form data is inherently a very local state, especially for Angular since ngModel binds to local component variables. The top devs that I know recommend keeping the data for the form localized to that component (ie just use ngModel with local variables). This is because un-submitted form data is almost never shared by various components across your whole application. When the user submits the form then you can dispatch an action with a payload containing the form data to a parent component, to the store, or even to an ngrx/effect to be posted to a server.