Passing parameters to an Angular 2 component

When it comes to passing a string parameter to my component, I need the flexibility to adjust the parameters of services based on the passed value. Here's how I handle it: In my index.html, I simply call my component and pass the required parameter.

<top [mode]="tree">Loading...</top>

To enable this functionality in my component, I first import Input from angular2/core.

import {Input, Component, OnInit} from 'angular2/core';

Then, within my component's class, I declare an input property for the mode.

@Input() mode: string;

However, when I attempt to access the passed parameter ('tree') using console.log(), I find that it's coming up as undefined.

console.log(this, this.mode);

https://i.stack.imgur.com/mHNPN.jpg

If you're interested in seeing the complete code snippet for the component file:

import {Http, HTTP_PROVIDERS} from 'angular2/http';
import {Input, Component, OnInit} from 'angular2/core';
import {ParticipantService} from '../services/participant.service';
import {orderBy} from '../pipes/orderby.pipe';

@Component({
    selector: 'top',
    templateUrl: 'dev/templates/top.html',
    pipes: [orderBy],
    providers: [HTTP_PROVIDERS, ParticipantService]
})
export class AppTopComponent implements OnInit {

    constructor (private _participantService: ParticipantService) {}

    errorMessage: string;
    participants: any[];
    @Input() mode: string;

    ngOnInit() {
        console.log(this, this.mode);
        this.getParticipants('top3');
        var self = this;
        setInterval(function() {
            self.getParticipants('top3');
        }, 3000);
    }

    getParticipants(public mode: string) {
        this._participantService.getParticipants(mode)
            .then(
                participants => this.participants = participants,
                error => this.errorMessage = <any>error
            );
    }

}

Answer №1

When utilizing `[...]`, the value you input must be an expression that is able to be evaluated.

Therefore, the variable tree needs to refer to a string that exists in the parent component.

If you wish to utilize the string tree, follow this format:

<top mode="tree">Loading...</top>

Please note that these parameters are not suitable for the root component. Refer to the following question for further information:

  • Angular 2 input parameters on root directive

Answer №2

To overcome the restriction Thierry mentioned, one possible solution is to utilize

constructor(private _userService: UserService, 
    elRef:ElementRef) {
  this.type=elRef.nativeElement.getAttribute('type');
}

Answer №3

Ensure that you wait for the template to be connected to the DOM before making any changes. To achieve this, it is recommended to utilize AfterViewInit in your implementation.

    export class TopAppComponent implements AfterViewInit{

    public ngAfterViewInit() {
        console.log(this, this.mode);
        this.fetchTopParticipants('top3');
        var self = this;
        setInterval(function() {
            self.fetchTopParticipants('top3');
        }, 3000);
    }
   }

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

What is my strategy for testing a middleware that accepts arguments?

Here is the middleware I am working with: function verifyKeys(expectedKeys: string[], req: Request): boolean{ if (expectedKeys.length !== Object.keys(req.body).length) return false; for (const key of expectedKeys) { if (!(key in req.body)) return ...

I am interested in learning how to utilize jQuery to decode JSON Unicode within a Select2 dropdown filtering system

I am currently utilizing Select2 JS and Datatables JS to handle data in JSON format. However, I encountered an issue where the value Animal & Veterinary is displayed differently in JSON as Animal \u0026amp; Veterinary, and on the Select2 filter as ...

Can a form be submitted using ViewChild in Angular5?

Can a form be submitted using ViewChild in Angular5? If so, how can it be achieved? I attempted to do this but was unsuccessful My Attempt: <form #form="ngForm" (submit)="submitForm(form)" novalidate> <input required type="text" #codeReques ...

Switching between Angular components with a button press

I'm looking to switch from one Angular component to another when a button is clicked. Specifically, I have two components: app and login. Upon clicking a button in `app.component.html`, I want to navigate to `login.component.html`. Here's what I& ...

Transform the JSON response into a map

I have a functioning code that I am looking to adjust. let table_specs = {'columns': [ {'name': 'Col1', 'width': 7, ....}, {'name': 'Col2', 'width': 8, . ...

What is preventing me from obtaining the select and input values?

I'm currently facing an issue where I am unable to retrieve the values of customInput and customSelect and store them in the state. The challenge arises when trying to integrate these components into a react dashboard material-ui setup. Strangely, whe ...

What can be done to address the issue of v-model select option onchange displaying the previously selected value or becoming stuck on a static value rather than updating

Whenever I navigate to the message page and select a device, the v-model selected value changes. However, if I go to the device or contact page, the v-model selected value remains unchanged or goes back to the last selected value. Below is the function in ...

What could be the reason for PhantomJS getting stuck when jQuery is invoked?

Currently, I am using PhantomJS 2.0.0 on a Mac OS X Yosemite: $ phantomjs --version 2.0.0 The script I have attached below seems to get stuck at the line where it calls $('h1').size(): system = require('system'); function usage() { ...

What is the best way to integrate a new unique identifier into an existing MongoDB document using NodeJS?

I am looking to add up a field in a document when I input a new entry that has a replicated unique id. This is the code I have so far: MongoClient.connect(process.env.MONGODB_URI || process.env.DB_CONNECTION, { useUnifiedTopology: true, useNewUrlParser ...

Using Material UI Slider along with Typescript for handling onChange event with either a single number or an

Just diving into Typescript and encountered an issue with a Material UI Slider. I'm trying to update my age state variable, but running into a Typescript error due to the typing of age being number and onChange value being number | number[]. How can I ...

Monaco utilized for Angular web-based code editing platform

We recently created an online code editor in our project using the Monaco editor. Our next goal is to integrate an Angular editor into this platform. To achieve this, we require NPM support to install dependencies directly from the editor. If anyone has ...

Tips for altering the browser tab color on a PC or Mac with HTML or JavaScript

While I am aware of the method to change theme colors on mobile devices using <meta name="theme-color" content=" #0000ffbb" />, I prefer browsing on my laptop. Are there ways to customize browser tab appearance using HTML or JS fo ...

passport.authenticate method fails due to empty username and password values

I seem to be making a simple mistake while following a tutorial. Even though I believe I have followed all the steps correctly, when I submit the login form, I get redirected to the "failureRedirect" page. When I checked the source code in the passport mod ...

In the Angular Google Maps API, is it possible to update the attributes of <agm-marker> directly within the TypeScript code?

Currently, I am fetching markers from the database and displaying them on a map using Angular Google Maps (AGM) by utilizing the <agm-marker> tag. In my code snippet below, you can see how I fetch and store the markers in an array named markers in t ...

Getting the current page name within the app.component.ts file in Ionic 3 - a simple guide

Is it possible to retrieve the current active page name within the app.component.ts file in Ionic without having to add code to any other pages? ...

AngularJS Reload Scenario: A new way to refresh and enhance

My current project involves the development of a mobile app where I am retrieving data from a REST GET call. Everything is running smoothly. However, I would greatly appreciate expert advice on how to seamlessly re-render this data if the user decides to ...

What could be the reason behind the unexpected behavior of my Bootstrap 3 carousel?

I'm attempting to replicate this visual effect in my own carousel, featuring semi-transparent images on the left and right sides. However, I'm encountering a negative result with my project when transitioning between slides at : here. This is th ...

Enhancing the visual appeal of a javascript canvas animation

I am facing a small issue and I want to incorporate an animation from: http://codepen.io/chuckeles/pen/mJeaNJ My main query is how can I modify it so that instead of dots, there would be small images? Which part of the code should I edit for this purpose? ...

Tips for dynamically passing a URL to a function using the onload event

I require assistance with passing a dynamic URL to a function. code onload="getImage('+ val.logo +');" onclick="loadPageMerchantInfo('+ val.merchant_id +'); The value of val.logo contains a URL such as: https://www.example.com/upload ...

Removing div elements containing specific text using jQuery

Hello everyone, I am trying to remove all divs that contain a specific part of a string. Does anyone know how I can do this? This is what my original HTML looks like: <div class="article-options_4"></div> And this is the new HTML structure, ...