What is the mechanism behind this straightforward PrimeNG Angular 2 illustration?

As a newcomer to Angular 2/4 coming from Java, I have some uncertainties regarding an Angular project utilizing PrimeNG components.

To kick things off, I followed an introductory video tutorial for setting up my first Angular 4 webapp with PrimeNG integration: https://www.youtube.com/watch?v=6Nvze0dhzkE

The example provided in the tutorial involves incorporating a PrimeNG calendar component as seen below:

<p-calendar [(ngModel)]="value"></p-calendar>
{{value | date:'dd.mm.yyyy'}}

In relation to this, I am slightly confused about the logic behind this implementation and how it could be refactored. It appears that the custom tags correspond to components, but please correct me if I am mistaken.

I assume the necessary PrimeNG code is located within the node_modules directory of my project, right?

Furthermore, modifications were made to the app.module.ts file:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import {CalendarModule} from 'primeng/primeng';
import {FormsModule} from '@angular/forms';
import {BrowserAnimationsModule} from '@angular/platform-browser/animations';


@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserAnimationsModule,
    BrowserModule,
    FormsModule,
    CalendarModule,
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

// ???
export class MyModel {
  value: Date;
}

My main confusion lies within the declaration of the MyModel class in the app.module.ts file:

export class MyModel { value: Date; }

It seems redundant as removing it did not affect the functionality of the project. So, what purpose does this line serve in my view?

<p-calendar [(ngModel)]="value"></p-calendar>

Initially, I assumed it would store user-input values into the 'value' field of the MyModel class, but it doesn't seem to work as expected. What am I overlooking here?

Additionally, is it possible to create a custom component like 'MyCustomCalendar' to use in my app.component.html view, associated with a <customtag> tag, containing...

  • ...the specified content.

  • ...a variable initialized with the selected date.

Is such customization feasible in Angular projects?

Answer №1

I'm attempting to address some of your inquiries, however, it's quite challenging without having a look at the complete code:

I believe that it is a component because, as far as I know, custom tags are associated with components, right?

Correct - It is indeed a component.

I suppose I don't have the code for this component but rather something I downloaded via npm, which should be in the node_modules directory of my project, correct?

Correct - You've likely executed something like

npm install primeng --save

This action downloads the entire primeng UI suite into your node_modules folder. In Angular, various parts of an application are bundled into one module. Within your app.module.ts file, you're importing the primeng CalendarModule from your node_modules folder. This module also contains the component you mentioned earlier (the calendar-component associated with the selector <p-calendar>)

So, what exactly does this line do in my view?

<p-calendar [(ngModel)]="value"></p-calendar>

It generates the p-calendar component in this section of your HTML. The [(ngModel)] binds the value property in your component to the p-calendar component. The value property must exist within the component to which your HTML belongs. This is a two-way binding. Essentially, when the value changes, p-calendar will be notified about it. Similarly, if p-calendar alters the value, the corresponding value inside your component will change as well.

  • Two-way binding uses the banana-in-a-box syntax --> [(ngModel)]=...
  • One way binding employs only brackets --> [ngModel]=...

Another question is, [...] Can I do something like this?

Yes, it's recommended to explore more tutorials or videos on Angular and refer to the official documentation for deeper understanding. It might be complex to clarify this detail here.

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