angular 5 display nested questions and answer show item under it parent item

Question

this is my server response for quetions and answers.. its a array.

[
    {
        \"id\": 1,
        \"product\": 1,
        \"user\": \"alex\",
        \"text\         


        

Answer 1

Accepted answer Working for one level question. If really want to work in nested scenario: Please check below option

  export class QuestionList
  {
    questions:Question[];
  }

  export class Question
  {
   text:string;
   answer:Answer;
   nextquestions:QuestionList;
 }

export class Answer
{
  text:string;
}


@Component({
 selector: 'question-view',
 template: `<ul>
        <li *ngFor="let q of questions">
          {{q.text}}:{{q.answer.text}}
          <question-view [questions]=q.nextquestions></question-view>
       </li></ul>`
   })


  export class QuestionViewComponent  {
  @Input() questions: any[];
 }

Answer 2

Try this HTML, where responses is as follows

responses = [
    {
        "id": 1,
        "product": 1,
        "user": "alex",
        "text": "is it ok?",
        "parent_id": null,
    },
    {
        "id": 2,
        "product": 1,
        "user": "john doe",
        "text": "yes its ok.",
        "publish": true,
        "parent_id": 1,
    },
      {
        "id": 3,
        "product": 1,
        "user": "shiva",
        "text": "how can i .. . .",
        "publish": true,
        "parent_id": null,
    },
]

<div *ngFor="let res of responses">
  <div *ngIf="res.parent_id === null">
    Ques : {{res.text}}
    <br/>
    Answers :
    <ng-container *ngFor="let res2 of responses">

       <div *ngIf="res2.parent_id === res.id">
         {{res2.text}}
       </div>
    </ng-container>
  </div>

</div>

Check this fiddle

Answer 3

If only has a response (not a response of response) you always can do

<div *ngFor="let q of questions>
   <!--only want to show the question, not the answer-->
   <div *ngIf="!q.parent_id> 
      {{q.user}}{{q.text}}
      <div *ngFor="let a of question.filter(t=>t.parent_id==q.id)>
          response:{{a.user}}{{a.text}}
      </div>
   <div>
</div>

or "map" the array to create a new list of question and answer

this.questionAndAndwers=this.question
          .filter(q=>!q.parent_id)
          .map(q=>{
               let answer=this.question.find(i=>i.parent_id==q.id)
               return {...q,
                       a_user:answer?answer.user:null,
                      a_text:answer?answer.text:null
                      ..others properties....
               }
          })

EDITED: completing the answer We can map too like

this.questionAndAndwers=this.question
          .filter(q=>!q.parent_id)
          .map(q=>{
               return {...q,
                       answers:this.question.filter(i=>i.parent_id==q.id)
               }
          });

Or better if there are reply of reply of reply... we can make a recursive function

getAnswers(questions:any,id:any)
  {
    return questions
           .filter(i=>i.parent_id==id)
           .map(q=>{
             return {...q,
                     answers:this.getAnswers(questions,q.id)}
           })
  }
//And
this.questionAndAndwers=this.getAnswers(this.question,null)

Then we can make a component

@Component({
  selector: 'app-question',
  template: `<div *ngFor="let q of questions">
              {{q.user}}{{q.text}}
              <app-question [questions]=q.answers></app-question>
           </div>`
})
export class QuestionComponent  {
  @Input() questions: any;
}

//In our app.component
<app-question [questions]="questionAndAndwers"></app-question>