Angular CLI, TypeError: Cannot read property 'value' of undefined

Question

I'm trying to get radio button value and send them to MySql database but i got an error that said TypeError: Cannot read property 'value' of undefined. I'm using Angular and express JS in this project. In the server side, the query is looks like this app.post('/post', ...){ let sql = 'INSERT INTO results(question1, question2, question3)values("'+req.body.question1+'", "'+req.body.question2+'", "'+req.body.question3+'")'; }. I already have the questions and the options in a json file.

//data.json

[{
  "surveyid": 101,
  "surveyname": "Vitamin",
  "createdby": "Dr. Sarah",
  "createddate": "16-01-2018",
  "question": [{
      "questionid": 1,
      "questiondesc": "Q-1?",
      "qno": 1,
      "alloptions": [{
          "options": "A",
          "answer": "Yes"
        },
        {
          "options": "B",
          "answer": "No"
        }
      ]
    },

    {
      "questionid": 2,
      "questiondesc": "Q_2?",
      "qno": 2,
      "alloptions": [{
          "options": "A",
          "answer": "Yes"
        },
        {
          "options": "B",
          "answer": "No"
        },
        {
          "options": "C",
          "answer": "Don't know"
        }
      ]
    },

    {
      "questionid": 3,
      "questiondesc": "Q_3",
      "qno": 1,
      "alloptions": [{
          "options": "A",
          "answer": "Yes"
        },
        {
          "options": "B",
          "answer": "No"
        }
      ]
    }
  ]
}]

And then i load all the questions and options into html template.

<form>
  <div *ngFor="let items of jsonData">
    <div *ngFor="let items2 of items.question">
      <label>{{items2.questionid}}. {{items2.questiondesc}}</label>
      <div *ngFor="let items3 of items2.alloptions; let idx=index">
        <div class="radio">
          <input type="radio" name="question{{items2.questionid}}" [value]="items3.answer"><b>{{items3.options}}</b>. {{items3.answer}}
        </div>
      </div><br>
    </div>
  </div>
  <div align="center">
    <button type="button" class="btn btn-sm btn-success" (click)="pushResults(question1.value, question2.value, question3.value)">SUBMIT</button>
  </div>
</form>

And here is the service and component

//service.ts
getJsonData(): Observable < any > {
  return this.http.get('../assets/data.json')
    .map((res: Response) => res.json())
    .catch((error: any) => Observable.throw(error.json().error || 'server returns error'))
}

pushResults(question1: string, question2: string, question3: string) {
  return this.http.post('http://localhost:8000/newPush', {
    question1: question1,
    question2: question2,
    question3: question3
  });
}

//component.ts
jsonData = [];
getJsonData() {
  this.AppService.getJsonData().subscribe(
    data => console.log('json', this.jsonData = data),
    error => console.log('server returns error')
  );
}

pushResults(question1: string, question2: string, question3: string) {
  this.AppService.pushResults(question1, question2, question3);
}

Can anyone help me with this, please? Please let me know if more snippets are needed.

Answered in this Link. Thank you.

Wira Xie
– Wira Xie

2018-01-19 05:59:53 +00:00
Commented Jan 19, 2018 at 5:59 — Wira Xie
– Wira Xie, Commented Jan 19, 2018 at 5:59

yurzui · Accepted Answer · 2018-01-19 04:39:02Z

Since you don't use angular forms you can obtain values through form elements collection:

First thing you need to do is to get hold of form element.

<form #myForm>

Now you can access the value of the elements like this:

form.elements['question1'].value

Native Form Example

Angular template driven form

1) Import FormsModule to your NgModule

import { FormsModule } from '@angular/forms';    

@NgModule({
  imports: [
    ...
    FormsModule
  ],
  ...
})
export class AppModule { }

2) Create property of type Array in your component

answers: string[] = [];

3) Change template like:

<form #form="ngForm">
  <div *ngFor="let items of jsonData">
    <div *ngFor="let items2 of items.question; let i = index">
      <label>{{items2.questionid}}. {{items2.questiondesc}}</label>
      <div *ngFor="let items3 of items2.alloptions; let idx=index">
        <div class="radio">
          <input type="radio" 
            name="question{{items2.questionid}}"
            [(ngModel)]="answers[i]"                     
            [value]="items3.answer"><b>{{items3.options}}</b>. {{items3.answer}}
        </div>
      </div><br>
    </div>
  </div>
  <div align="center">
    <button type="button" class="btn btn-sm btn-success" (click)="pushResults(form.value)">
      SUBMIT
    </button>
  </div>
</form>
<pre>{{ form.value | json }}</pre>

Template driven Form Example

Angular model driven Form

1) Import ReactiveFormsModule to your NgModule

import { ReactiveFormsModule} from '@angular/forms';    

@NgModule({
  imports: [
    ...
    ReactiveFormsModule
  ],
  ...
})
export class AppModule { }

2) Create FormGroup in your component

import { FormGroup, FormBuilder } from '@angular/forms';

@Component({
  ...
})
export class AppComponent {

  form: FormGroup;
  ...

  constructor(private fb: FormBuilder) {}

  ngOnInit() {
    this.form = this.fb.group({
      question1: '',
      question2: '',
      question3: ''
    })
  }

  pushResults(formValue) {
    console.log(formValue.question1, formValue.question2, formValue.question3);
  }
}

3) Change template like:

<form [formGroup]="form">
  <div *ngFor="let items of jsonData">
    <div *ngFor="let items2 of items.question; let i = index">
      <label>{{items2.questionid}}. {{items2.questiondesc}}</label>
      <div *ngFor="let items3 of items2.alloptions; let idx=index">
        <div class="radio">
          <input type="radio" 
              name="question{{items2.questionid}}"  
              formControlName="question{{i+1}}"
              [value]="items3.answer"><b>{{items3.options}}</b>. {{items3.answer}}
        </div>
      </div><br>
    </div>
  </div>
  <div align="center">
    <button type="button" class="btn btn-sm btn-success" (click)="pushResults(form.value)">
      SUBMIT
  </button>
  </div>
</form>
<pre>{{ form.value | json }}</pre>

Model driven Form Example

If you want to do only one form you do not need to import FormsModule or ReactiveFormsModule but for scale project I would suggest using one of angular built-in methods.

Vishal · Accepted Answer · 2018-01-19 03:53:04Z

1

Don't use this inside templates. this is only meant to be used inside components. Because inside templates all the variables you use are meant to be component/class variables. Local variables can't be referenced in templates. Directly access the member variable as follows:

(click)="pushResults(question1.value, question2.value, question3.value)"

answered Jan 19, 2018 at 3:53

Vishal

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2 Comments

Wira Xie Over a year ago

thanks, updated my code, but still got the same error.

Vishal Over a year ago

check the answer to your other question: stackoverflow.com/a/48334015/5346095 It may help. Else console the values your pushing function receives. Share the same in plunk.

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