How to set value in array form with Angular

Question

I want to set value in array like this:

this.form.controls[name].setValue('name')

but I am working with array forms, and this is not working, even if I pass an array index explicitly

for example, this is my form array and I want to do is to set value in a function

user: FormGroup;
users: FormGroup;

constructor(private fb: FormBuilder) {}
ngOnInit() {
  this.user = this.buildGroup();
  this.users = this.fb.group({
    data: this.fb.array([this.user])
  });
}
get fData() {
  return this.users.get('data') as FormArray;
}
buildGroup() {
  return this.fb.group({
    name: ['', [Validators.required, Validators.minLength(2)]],
    account: this.fb.group({
      email: ['', Validators.required],
      confirm: ['', Validators.required]
    })
  });
}
setValue(index) {
  // This doesn't work
  this.fData[index].controls[name].setValue('name')
}
onSubmit() {
  this.fData.push(this.buildGroup());
  const {valid, value} = this.fData;
  console.log(valid, value);
}

Answer 1

For arrays, you need to use setControl. Something like this:

    this.productForm = this.fb.group({
        productName: ['', [Validators.required,
                           Validators.minLength(3),
                           Validators.maxLength(50)]],
        productCode: ['', Validators.required],
        starRating: ['', NumberValidators.range(1, 5)],
        tags: this.fb.array([]),
        description: ''
    });

    ...

    // Update the data on the form
    this.productForm.patchValue({
        productName: this.product.productName,
        productCode: this.product.productCode,
        starRating: this.product.starRating,
        description: this.product.description
    });
    this.productForm.setControl('tags', this.fb.array(this.product.tags || []));

Answer 2

Here is what I have done to set value manually in formArray's specific form control and worked for me. I have formArray named as bundleDetails.

this.formBuilderObj['bundleDetails'] = 
this.formBuilder.array([this.createBundleItem()]);
   
createBundleItem(): FormGroup {
    return this.formBuilder.group({
        bsku: ['', Validators.required],
        bqty: ['', Validators.required],
        bprice: ['', Validators.required]
    });
}

Method to set bsku control's value (where index is [formGroupName]="i" passed from an HTML file).

setSku(sku: string, index: number) {
   const faControl = 
   (<FormArray>this.pmForm.controls['bundleDetails']).at(index);
   faControl['controls'].bsku.setValue(sku);
}

Answer 3

If you're getting the error "ERROR Error: Cannot find control with path: 'addresses -> 0 -> addressType'" or something similar, it's most likely cause you're passing the values in but your html template is expecting values along with a control name.

To resolve this, iterate over each item in your array, and create a new form group instance for each value - based on what your view is expecting - then push to a new array variable, which we then set in our form.

See code below:

var tagsArray = [];
this.product.tags.forEach(product => tagsArray.push(this.fb.group({tag: [product.tag, [Validators.required]]})));
this.productForm.setControl('tags', this.fb.array(tagsArray || []));

Referenced in view like so:

<div class="tag" *ngFor="let t of tags.controls; let i = index" [formGroupName]="i" class="mb-2">
      <input type="text" formControlName="tag" placeholder="Tag name" class="primary_input">
       <button mat-icon-button (click)="deleteTag(i)">
           <mat-icon>clear</mat-icon>
       </button>
 </div>

This lets you load previous results while enabling the ability to add more values and validate user input.

Hope this helps.