1. Introduction

1.1 Goal of the Tutorial

This tutorial aims at providing a detailed guide on how to create and use custom pipes in Angular. Pipes are powerful tools in Angular that help in transforming data for user interfaces.

1.2 Learning Outcomes

By the end of this tutorial, you will be able to:
- Understand what pipes are and why they are important.
- Create your own custom pipes.
- Use these custom pipes within your Angular applications.

1.3 Prerequisites

Before starting this tutorial, you should have basic knowledge of:
- JavaScript/TypeScript.
- Angular (Components, Modules).

2. Step-by-Step Guide

2.1 Understanding Pipes

In Angular, a Pipe takes in data as input and transforms this data into a desired output. For example, Angular provides built-in pipes for date formatting, uppercase, lowercase, decimal, percent, and more.

2.2 Creating a Custom Pipe

To create a custom pipe, you need to create a new TypeScript file and decorate a class with @Pipe.

Here are some best practices:
- Always import Pipe and PipeTransform from @angular/core.
- The name property of the @Pipe decorator is used to reference the pipe within your templates.

3. Code Examples

3.1 Creating a Custom Pipe

// Import Pipe and PipeTransform from Angular Core
import { Pipe, PipeTransform } from '@angular/core';

// Use the @Pipe decorator to define the pipe name
@Pipe({name: 'customPipe'})

// Implement PipeTransform interface
export class CustomPipe implements PipeTransform {
  // Implement transform method
  transform(value: any, ...args: any[]): any {
    // Transform the input data and return
    return value;
  }
}

This pipe doesn't do anything yet, but it's a valid custom pipe. You would replace return value; with your transformation logic.

3.2 Using a Custom Pipe

First, you need to declare your pipe in your Angular Module.

import { NgModule } from '@angular/core';
import { CustomPipe } from './custom.pipe';

@NgModule({
  declarations: [
    CustomPipe
  ],
  exports: [
    CustomPipe
  ]
})
export class AppModule { }

You can now use your custom pipe in your templates.

<p>{{ 'Hello, World!' | customPipe }}</p>

4. Summary

In this tutorial, we have learned about Angular Pipes, how to create a custom pipe, and how to use it in an Angular application. The next step would be to create more complex pipes capable of handling more advanced data transformations.

Additional resources:
- Angular Official Pipes Documentation
- Angular Built-In Pipes

5. Practice Exercises

5.1 Exercise 1: Simple Transformation Pipe

Create a custom pipe that transforms a string input into Pig Latin.

5.2 Solution and Explanation

@Pipe({name: 'pigLatin'})
export class PigLatinPipe implements PipeTransform {
  transform(value: string): string {
    return value.split(' ').map(word => word.slice(1) + word[0] + 'ay').join(' ');
  }
}

This pipe takes a string, splits it into words, rearranges each word to form Pig Latin, and then joins the words back together.

5.3 Exercise 2: Complex Transformation Pipe

Create a custom pipe that takes an array of numbers and returns an array of the squares of those numbers.

5.4 Solution and Explanation

@Pipe({name: 'squareNumbers'})
export class SquareNumbersPipe implements PipeTransform {
  transform(values: number[]): number[] {
    return values.map(value => value * value);
  }
}

This pipe takes an array of numbers, squares each number, and returns the new array.