Using Custom Pipes in a Component Class in Angular

It’s easy to create custom pipes to use in your templates to modify interpolated values. You don’t have to duplicate your code if you want to also use a pipe’s functionality in a component class. All you have to do really is inject the pipe like a service, and then call its transform method.

The following works for any Angular 2+ app.

Say we have a custom CapitalizePipe that capitalizes every word that’s longer than 2 characters:

capitalize.pipe.ts

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({ name: 'capitalize' }) export class CapitalizePipe implements PipeTransform { transform(value: string, args?: any): any { return value.split(' ').map(word => { return word.length > 2 ? word[0].toUpperCase() + word.substr(1) : word; }).join(' '); } }

Now, given that your pipe has been properly added to your module’s declarations, you can inject it in a component’s class like this:

app.component.ts

// ... import { CapitalizePipe } from './capitalize.pipe';

@Component({ selector: 'app-root', templateUrl: './app.component.html', styleUrls: ['./app.component.css'], providers: [ CapitalizePipe ] }) export class AppComponent {

constructor(private capitalize: CapitalizePipe) {}

// ... }

And to use it you simple call transfom on the injected instance:

onSubmit(value) { this.data = this.capitalize.transform(value); // ... }

Simple as that! Now you can define logic in custom pipes that can be reused directly in component classes without duplicating code.

Published: April 18, 2017