Angular Form add input field based on dropdown value

1
votes

Does anyone have idea how to show additional input field based on select element value and push value into existing object?

There is a dropdown select element with change directive 

<div class="col-sm-4">
  <select class="form-control mt-2" id="field_countries" name="country" #t formControlName="country" (change)="countryChanged(t.value)">
    <option [value]="country.name" *ngFor="let country of countries"> {{ country.name }} </option>
  </select
</div>

and countryChanged event

countryChanged(value) {
  this.selectedCountry = value;
  console.log(this.selectedCountry);
}

so I'm trying to add new input field based on selected value:

<div class="col-sm-4" *ngIf="selectedCountry == 'Mexico'">
  <input type="text" class="form-control" name="remark" formControlName="remark" maxlength="200" />
</div>

but I don't know how to show input field and push value only for object which value is selected for, so the result would be enter image description here

equivalent to [{person: 'John', country: 'USA'}, {person: 'Pablo', country: 'Mexico', remark: 'Some data'}, {person: 'Michelle', country: 'France'}]

Stackblitz

2
angulartypescriptangular-formsformarrayangular-formbuilder
Well, if the values are the same for each person and each country... I think you should use an external form. This way, the function controlling the remark field will only function with the right row. - RoadEx
You might just want to show/hide the remark field by CSS using the + or ~ selector. - Zammy

2 Answers

1
votes

Match current value with template ref variable that u have declared as "t" like this:

*ngIf="t.value == 'Mexico'" here:

<div class="col-sm-4" *ngIf="t.value == 'Mexico'">
  <input type="text" class="form-control" name="remark" formControlName="remark" maxlength="200" />
</div>

and then you can remove blank attributes in submit function with some ES6:

  onSubmit() {
    this.persons = this.selectForm.get('persons') as FormArray;
    const temp: any = this.persons.value;
    temp.forEach((v) => {
      Object.keys(v).forEach((key) => (v[key] == '') && delete v[key]);
    })
    console.log(temp)
  }

Stackblitz

1
votes

I modified your stack blitz a little: See it here: https://stackblitz.com/edit/select-populate-values-kyirzw?file=app%2Fapp.component.ts

While Initilizing the FormGroup, I didn't add the remark FromControl by Default.

  getFormGroupByN(n: number) {
  let result = [];
  for (let i = 0; i < n; i++) {
    result.push(this.formBuilder.group({
      'person': '',
      'country': ''
    })
    );
  } // for end 

  return result;
}

I modified the countryChanged() method of yours, which now also accepts an index of the FormArray. Now whenever I see that the country selected was Mexico I add a FormControl remark to that particular FormGroup at that index.

countryChanged(value, i) {
  this.selectedCountry = value;
  // this.getFormGroupByN(this.personsData.length);  // why were you calling this again?
  if (value == "Mexico") {
    let temp =  <FormGroup>(<FormGroup>this.selectForm.get('persons')).controls[i];
    temp.addControl('remark', new FormControl(''));
  }
}

The HTML for showing Input box for Remarks is now checking for the presence of the remark formContrl instead of the CountryName

<div class="col-sm-4" *ngIf="selectForm.get('persons').controls[i].get('remark')">
   <input type="text" class="form-control" name="remark" formControlName="remark" maxlength="200" />
</div>