Javascript - I'm trying to generate form control dynamically in angular forms & i'm facing that error in console "TypeError: feature_r5.get is not a function"

Veronika
May 22, 2023
261 views
0 votes
2 Answers

I’m trying to generate form controls dynamically on click of a button in Angular v14 html template i generate it but i’m facing that error in console.

ERROR TypeError: feature_r5.get is not a function
 at PostAdvComponent_div_40_Template

Html template code

<div id="features" class="tab-pane mytab-pane">
            <div class="form-group">
                <button type="button" class="btn btn-primary" (click)="addFeatureButtonClick()">Add</button>
            </div>

            <div formArrayName="features" *ngFor="let feature of advForm.get('features')?.value; let i = index">
                    <div attr.formGroupName="{{i}}">
                        <div class="form-group" [ngClass]="{'has-error' : feature.get('fName').invalid &&
                                                                           feature.get('fName').touched}">
                            <div class="input-group">
                                <span class="input-group-prepend">
                                    <label class="input-group-text"><strong>Features</strong></label>
                                </span>
                                <input type="text" id="{{'fName'+i}}" name="fName" class="form-control" placeholder="Features"
                                    formControlName="fName"/>
                            </div>
                            <span class="help-block" *ngIf="feature.get('fName').errors.required &&
                                                            feature.get('fName').touched">
                                Feature is required
                            </span>
                        </div>
                    </div>
            </div>
        </div>

Answers

- Dhana
- May 22, 2023 at 5:31 am
- 0 votes
0
The error you’re encountering, ERROR TypeError: feature_r5.get is not a function, suggests that the feature object you’re using in your template doesn’t have a get function. This error typically occurs when you try to access a property or invoke a method on an undefined or null value.

In your template, you’re using feature.get(‘fName’) multiple times. The issue might be with the way you’re accessing the feature object within the *ngFor loop.

To fix this error, make sure that advForm.get(‘features’)?.value is not null or undefined. Additionally, ensure that each feature object within the loop is a FormGroup instance, as it should have a get method.

Here are a few steps you can take to troubleshoot and resolve the issue:

Verify that advForm.get(‘features’)?.value is properly populated with an array of FormGroup instances.
Make sure that feature within the *ngFor loop refers to a FormGroup object.
Double-check that the fName form control exists within each feature FormGroup.

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- Eliseo
- May 22, 2023 at 8:59 am
- 0 votes
0
1. Not iterate over the values (else when you change an input, Angular redraw and you loose the focus):
```
*ngFor="let feature of advForm.get('features')?.value;.." //<--WRONG
```
  You need use a "getter"
```
get featureFormArray()
{
   return this.form.get('features') as FormArray
}
```
  and iterate over "controls"
```
*ngFor="let feature of featureFormArray.controls;.." //<--WRONG
```
2. formGroupName is not an attribute, else a directive, so
```
<div attr.formGroupName="{{i}}"> //<--WRONG
<div [formGroupName]="i"> //<---OK
```
3. When manage fromGroup of formArray I like more use this structure
  (the formArrayName outside the loop, the same tag in loop, the
  formGroupName):
```
<form [formGroup]="form">
   <div formArrayName="features">
      <div *ngFor="let feature of featuresFormArray.controls;let i=index"
                   [formGroupName]="i">
         ...yours inputs..
         <input formControlName="fName">
      </div>
   </div>
</form>
```
4. You need use the safe operator (see the ? before the dot) after the
  .get else you have an error of "possible null or undefined"
```
feature.get('fName')?.invalid && feature.get('fName')?.touched
```
5. Same before when you check errors.required
```
*ngIf="feature.get('fName')?.errors?.required
```
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