IOS - RadListView Fatal Javascript exception

3 posts, 1 answers
  1. Anurag
    Anurag avatar
    27 posts
    Member since:
    Apr 2016

    Posted 12 Sep Link to this post

    In my NativeScript angular project I am using a radlistview to display a list of messages from a firebase backend.  In Android the list item is displaying correctly however in IOS I am getting the following error and the application is terminated:

    CONSOLE WARN file:///app/tns_modules/tns-core-modules/application/application.js:212:26: Fatal JavaScript exception - application has been terminated.
    file:///app/tns_modules/nativescript-telerik-ui/listview/listview.js:1311:20: JS ERROR TypeError: undefined is not an object (evaluating 'type.toLowerCase')


    I am using the latest version of the nativescript-telerik-ui 3.1.0 and tns 3.2.

    My code for the template, component and service is as follows, Please let me know what I  need to change.  


    <GridLayout rows="*" class="m-x-10">
            <RadListView [items]="this.messagesForView" [itemTemplateSelector]="templateSelector">
                <ng-template tkTemplateKey="testPrint" let-item="item">
                    <!--For testPrint messages-->
                    <GridLayout rows="auto auto" columns="auto *">
                        <Label row="0" col="0" text="" class="fa p-t-4 m-y-5"></Label>
                        <Label row="0" col="1" [text]="'Your item ' + item.testName + 'is ready for download at ' + item.testLink"></Label>
                        <Label row="1" col="1" text="11:50" horizontalAlignment="right"></Label>
                <ng-template tkTemplateKey="otherMessage" let-item="item">
                    <!--For Other Messages-->
                    <GridLayout rows="auto auto" columns="auto *">
                        <Label row="0" col="0" text="" class="fa p-t-4 m-y-5"></Label>
                        <Label row="0" col="1" [text]="item.body"></Label>
                        <Label row="1" col="1" text="13:10" horizontalAlignment="right"></Label>



    import { AfterContentInit, Component, OnInit, OnDestroy } from "@angular/core";
    import { NavigationExtras, Router } from "@angular/router";
    import { RouterExtensions } from "nativescript-angular";
    import { android } from "application"; // THis is to import application for handleing back button.
    import { Subscription } from "rxjs/Rx";
    import { Page } from "ui/page";
    import { Location } from "@angular/common";
    //import ui elements
    import scrollViewModule = require("ui/scroll-view");
    // import htmlViewModule = require("ui/html-view");
    import { ListViewEventData, RadListView } from "nativescript-telerik-ui/listview"; //This import is for rad list and event data on radList.
    import { topmost } from "ui/frame"; //To catch the rad list component as view.
    import { View } from "ui/core/view"; //To use a component as a View.
    import { isTablet } from "../shared/device-constant/device.constant";
    import { UserStatusService } from "../services/userStatus.service";
    import { FirebaseMessagingService } from "../services/firebase-messaging.service";
    import { AndroidBAckButtonHandlerService } from "../services/androidBackButtonHandler.service";
    import { ObservableArray } from "data/observable-array";
        selector: "messaging",
        styleUrls: [(isTablet ? '../tablet.css' : '../phone.css')],
        templateUrl: "./messaging.component.html",
    export class MessagingComponent implements OnInit, OnDestroy {
        uid: string;
        private backButtonHandler: Subscription;
        public isTablet: boolean;
        public messagesForView: ObservableArray<any>;
        private _templateSelector: (item: any, index: number, items: any) => string;
        public messagesSubscriber: Subscription;
        constructor(private router: Router,
            private routerExtensions: RouterExtensions,
            private location: Location,
            private userStatusService: UserStatusService,
            private firebaseMessagingService: FirebaseMessagingService,
            private page: Page,
            private androidBAckButtonHandlerService: AndroidBAckButtonHandlerService) {
        public ngOnInit() {
            this.messagesForView = new ObservableArray();
            this._templateSelector = this.templateSelectorFunction;
   = true;
            this.messagesSubscriber = this.firebaseMessagingService.messagesReceived.subscribe((currentMessages) => {
                this.messagesForView.push.apply(this.messagesForView, currentMessages);
            if (this.firebaseMessagingService.getMessages() !== undefined) {
                this.messagesForView = JSON.parse(this.firebaseMessagingService.getMessages());
            } else {
                const welcomeMessage = {
                    type: "otherMessage",
                    testName: "Trial Test",
                    testLink: "Trial Link",
                    title: "Welcome",
                    body: "Hello",
            //Subscribing android back button event emitter.
            this.backButtonHandler = this.androidBAckButtonHandlerService.detailTestBackHandler.subscribe((status) => {
                console.log("Back button pressed on detail test component and the status is: " + JSON.stringify(status));
        get dataItems(): ObservableArray<any> {
            return this.messagesForView;
        get templateSelector(): (item: any, index: number, items: any) => string {
            return this._templateSelector;
        set templateSelector(value: (item: any, index: number, items: any) => string) {
            this._templateSelector = value;
        public templateSelectorFunction = (item: any, index: number, items: any) => {
            return item.messageType;
        public ngOnDestroy() {
            if (android) {
                console.log("Back button handler is unsubscribed !!");



    import { Injectable, EventEmitter, NgZone } from "@angular/core";
    import firebase = require("nativescript-plugin-firebase");
    import { Observable } from 'rxjs/Observable';
    import { BehaviorSubject } from 'rxjs/BehaviorSubject';
    import 'rxjs/add/operator/share';
    import { setString, getString, remove } from "application-settings";
    import { ObservableArray } from "tns-core-modules/data/observable-array";
    export class FirebaseMessagingService {
        public messagesReceived: BehaviorSubject<any> = new BehaviorSubject({});
            private ngZone: NgZone,
        ) {
        // Get the User's messages
        public getMessageFromFirebase(): void {
            console.log("I have come to get my messages");
                (message) => {
                    if (message) {
                        //create message object
                        let currentMessages = new ObservableArray();
                        const newMessage = this.createMessageObject(message);
                        if (this.getMessages() !== undefined) {
                            currentMessages.push.apply(currentMessages, JSON.parse(this.getMessages()));
                        console.log("Current Messages is " + currentMessages);
                        console.log("After pushing Current Messages is " + currentMessages);
        createMessageObject(message) {
            console.log("Message Data type is" + message.type);
            console.log("Type of the message type is" + typeof (message.type));
            if (message.type === "testPrint") {
                const messageObject = {
                    messageTestName: message.title,
                    messageType: message.type,
                    messageBody: message.body,
                    messageTestLink: message.testLink,
                return messageObject;
            else {
                const messageObject = {
                    messageTitle: message.title,
                    messageType: message.type,
                    messageBody: message.body,
                return messageObject;
        setMessages(storedMessages: string) {
            setString('storedMessages', (storedMessages));
        getMessages() {
            return getString('storedMessages');
        removeMessages() {


    Thank you.

  2. Answer
    Deyan avatar
    2147 posts

    Posted 12 Sep Link to this post

    Hi Anurag,

    Thanks for writing.

    I think the reason for this error is that in your template selector you are returning `undefined` as a value for the template type:

    public templateSelectorFunction = (item: any, index: number, items: any) => {
            return item.messageType;

    I see from  your code that the property representing the template type is called `type` not `messageType`.

    I hope this is helpful.

    Progress Telerik
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  3. Anurag
    Anurag avatar
    27 posts
    Member since:
    Apr 2016

    Posted 12 Sep Link to this post

    Many Thanks Deyan! That was indeed the problem
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