Initialise static custom class inside other custom class

Hello! I’m new to Ionic 2 and trying to initialise static custom class inside other custom class:
I have a Question class which is composed of an Array of QuestionItems. My plan is to use each Item in a Checkbox or Radio button List

This is my testQuestion.ts:

export class Question {
	questionId: number;
	questionText: string;
	itemNumber: number;
	itemList: Array < QuestionItem > ;

    		questionId: number,
    		questionText: string,
		itemNumber?: number,
		itemList ? : Array < QuestionItem >
 ) { 
    		this.questionId = questionId; 
    		this.questionText = questionText;
		this.itemNumber = itemNumber;
		this.itemList = itemList;

    export class QuestionItem {
    	itemID: number;
    	itemText: string;
    	isChecked: boolean;
    		itemText: string
    		itemID?: number,
    		isChecked?: boolean
    		this.itemID = itemID;
    		this.itemText = itemText;
    		this.isChecked = false;


import {Component} from '@angular/core';
import {NavController} from 'ionic-angular';
import {Question } from './../../classes/Test/testQuestion';

  templateUrl: 'build/pages/test/test.html',

export class TestPage { 
//My question is how I assign the parameter QuestionItem correctly inside Question

 question00 = new Question(1,'Do you have at least 3 GCSEs?',2,['Yes','No']  );
//                                                                ^^

  constructor(private navController: NavController) {



<ion-content padding class="test">


    <ion-item *ngFor="let item of question00.itemList">      
        <ion-checkbox class="checklist"></ion-checkbox>




Thank you in advance!

Why does QuestionItem need to be a class instead of an interface? I would just do something like this:

interface QuestionItem {
  itemText: string;
  itemID?: number;
  isChecked?: boolean;

[{itemText: 'Yes'}, {itemText: 'No'}]