nested custom FormArray component doesn't bind with child form with FormArrayName

Question

I tried to have 2 nested forms using CVA. the problem is the second from isn't initialized with data when I bind it to a formControl.

Stackblitz

I have MAIN-FORM:

this.requestForm = this.fb.group({
  garageId: 0,
  routes: new FormArray([
    new FormGroup({
      addressPointId: new FormControl,
      municipalityId: new FormControl,
      regionId: new FormControl,
      rvId: new FormControl,
      sequenceNumber: new FormControl,
      settlementId: new FormControl,
      regionName: new FormControl,
      municipalityName: new FormControl,
      settlementName: new FormControl,
      description: new FormControl,
    })
  ]),
  endDateTime: 0,
});

In main-form html I bind routes to with formArrayName.

 <app-cva-form-array formArrayName="routes"></app-cva-form-array>

Component CVA-FORM-ARRAY has.

form = new FormArray([
new FormGroup({
  addressPointId: new FormControl,
  municipalityId: new FormControl,
  regionId: new FormControl,
  rvId: new FormControl,
  sequenceNumber: new FormControl,
  settlementId: new FormControl,
  regionName: new FormControl,
  municipalityName: new FormControl,
  settlementName: new FormControl,
  description: new FormControl,
})
]);

Everything from here works just fine. I bind each formGroup in the array to child component CVA-FORM.

<app-cva-form [formControl]="route" (blur)="onTouched()"></app-cva-form>

CVA-FORM for each formGroup I created separate component in case I want to use component itself not the whole array.

  form: FormGroup = new FormGroup({
    regionName: new FormControl,
    regionId: new FormControl,
    municipalityName: new FormControl,
    municipalityId: new FormControl,
    sequenceNumber: new FormControl,
    settlementName: new FormControl,
    settlementId: new FormControl,
    addressPointId: new FormControl,
    description: new FormControl,
    rvId: new FormControl,
  });

the main-form <--to--> app-cva-form-array binding doesn't work for some reason.

The idea of these forms comes from kara's talk on angulaconnect. here are her slides.

help plz!

Answer 1

When you use "custom Form Control", you need take account that you feed the cursom Form Control with a Form Control (not FormArray, not FormGroup). The FormControl has as value an array or an object, but you need not confussed about this.(*)

You can see in work in stackblitz

That's your form is like

//in main.form
this.requestForm = new FormGroup({
  garageId: new FormControl(0),
  routes: new FormControl(routes), //<--routes will be an array of object
  endDateTime: new FormControl(0)
})

//in cva-form-array
this.form=new FormArray([new FormControl(...)]); //<-this.form is a 
                             //formArray of FormControls NOT of formGroup

//finally in your cva-form
this.form=new FormGroup({});
this.form=formGroup({
      addressPointId: new FormControl(),
      municipalityId: new FormControl(),
      ...
})

I've create a const to export to simply the code. MY const expor is

export const dataI = {
  addressPointId: "",
  municipalityId: "",
  regionId: "",
  rvId: "",
  sequenceNumber: "",
  settlementId: "",
  regionName: "",
  municipalityName: "",
  settlementName: "",
  description: "",
}

So, in mainForm we have

  ngOnInit() {
    let routes:any[]=[];
    routes.push({...dataI});
    this.requestForm = new FormGroup({
      garageId: new FormControl(0),
      routes: new FormControl(routes),
      endDateTime: new FormControl(0)
    })
  }
<mat-card [formGroup]="requestForm" style="background: #8E8D8A">
    <app-cva-form-array formControlName="routes"></app-cva-form-array>
</mat-card>

In cvc-form array create the formArray when we give value

  writeValue(v: any) {
    this.form=new FormArray([]);
    for (let value of v)
        this.form.push(new FormControl(value))

    this.form.valueChanges.subscribe(res=>
    {
      if (this.onChange)
        this.onChange(this.form.value)
    })
  }

    <form [formGroup]="form" >
        <mat-card *ngFor="let route of form.controls; 
            let routeIndex = index; let routeLast = last;">
           <button (click)="deleteRoute(routeIndex)">
             cancel
           </button>
           <app-cva-form [formControl]="route" (blur)="onTouched()"></app-cva-form>
      </form>

Finally, the cva-form

  writeValue(v: any) {
    this.form=new FormGroup({});
    Object.keys(dataI).forEach(x=>{
      this.form.addControl(x,new FormControl())
    })

    this.form.setValue(v, { emitEvent: false });
    this.form.valueChanges.subscribe(res=>{
       if (this.onChanged)
        this.onChanged(this.form.value)
    })
  }

<div [formGroup]="form">
  <mat-form-field class="locationDate">
    <input formControlName="regionName">
    <mat-autocomplete #region="matAutocomplete" 
      (optionSelected)="selectedLocation($event)">
      <mat-option *ngFor="let region of regions" 
      [value]="region">
        {{region.regionName}}
      </mat-option>
    </mat-autocomplete>
  </mat-form-field>
  <mat-form-field class="locationDate">
    <input formControlName="municipalityName" 
      [matAutocomplete]="municipality"
      (blur)="onTouched()"
      [readonly]="checked || this.form.value.regionId < 1">
   ....
   </form>

(*) Yes, we are used to seeing that a FormControl has as a value a string or a number, but no one forbids us that the value is an object or an array (for example, ng-bootstrap DatePicker stores an object {year: .. month: .., day ..}, mat-multiselect stores an array, ...)

Update Of course we can feed our control with data from a service or similar. The only thing we must take account is how we give the data. As usually I like make a function that received a data or null and return a FormControl

  getForm(data: any): FormGroup {
    data = data || {} as IData;
    return new FormGroup({
      garageId: new FormControl(data.garageId),
      routes: new FormControl(data.routes),
      endDateTime: new FormControl(data.endDateTime)
    })
  }

where IData is an interface

export interface IData {
  garageId: number;
  routes: IDetail[];
  endDateTime: any
}

and IDetail another interface

export interface IDetail {
  addressPointId: string;
  ...
  description: string;
}

Then we can have a complex data like (sorry for the large object)

let data = {
  garageId: 1,
  routes: [{
    addressPointId: "adress",
    municipalityId: "municipallyty",
    regionId: "regionId",
    rvId: "rvId",
    sequenceNumber: "sequenceNumber",
    settlementId: "settlementId",
    regionName: "regionName",
    municipalityName: "municipalityName",
    settlementName: "settlementName",
    description: "description",
  },
  {
    addressPointId: "another adress",
    municipalityId: "another municipallyty",
    regionId: "another regionId",
    rvId: "another rvId",
    sequenceNumber: "another sequenceNumber",
    settlementId: "another settlementId",
    regionName: "another regionName",
    municipalityName: "another municipalityName",
    settlementName: "another settlementName",
    description: "another description",
  }],
  endDateTime: new Date()
}

Then only need make

this.requestForm = this.getForm(data);

The stackblitz if updated