Angular Custom Pipes

Overview

In Angular, pipes are used to transform data before displaying it in the view. While Angular provides several built-in pipes such as uppercase, date, currency, etc, it is often necessary to create custom pipes to implement application-specific transformations. Custom pipes in Angular allow for complex data transformations to be easily reused across your application.

Syntax

Creating a custom pipe in Angular involves defining a new class with the @Pipe decorator, along with an associated transform function:

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

@Pipe({
  name: 'customPipe'
})
export class CustomPipe implements PipeTransform {
  transform(value: any, arg1: any, arg2: any): any {
    // transform logic goes here
  }
}

Example

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

@Pipe({
  name: 'appDoubler'
})
export class DoublerPipe implements PipeTransform {
  transform(value: number): number {
    return value * 2;
  }
}

<!-- Usage in Component Template -->
<div>
  {{ 5 | appDoubler }} <!-- Result: 10 -->
  {{ value | appDoubler }} <!-- Result: doubled value of "value" variable -->
</div>

Output

In the above example, the custom pipe DoublerPipe doubles the input value, so the output of 5 | appDoubler will be 10.

Explanation

In Angular, a custom pipe is created by defining a new class with the @Pipe decorator and implementing the PipeTransform interface in order to define the transform function which manipulates the input data.

Use

Custom pipes can be used in Angular applications to perform any kind of data transformations. They are particularly useful when dealing with complex or repeated data transformations that need to be reused across multiple components.

Important Points

• Custom pipes are defined using the @Pipe decorator and must implement the PipeTransform interface.
• The transform function implements the actual data transformation logic.
• The name property of the @Pipe decorator specifies the name of the custom pipe that can be used in templates.
• Custom pipes are used in templates using the pipe operator |.

Summary

Angular custom pipes provide a powerful and flexible way to transform data in your application templates. By creating your own custom pipes, you can encapsulate complex data transformations in a reusable manner, making your code more modular and easier to maintain.