README

A Pipeline / Chain of Responsibility design pattern implementation based on Laravel's Pipeline implementation.

A Pipeline is an object that accepts input data and sends it through a series of handlers (or "pipes") — which are functions, closures, and/or classes — to get a result at the end.

flowchart LR
	input[Input data]
	subgraph Pipeline
		pipe1[Pipe 1]
		pipe2[Pipe 2]
		pipe3[Pipe 3]

		pipe1 --> pipe2
		pipe2 --> pipe3
	end
	output[Output data]

	input --> pipe1
	pipe3 --> output

Installation
Prerequisites
Getting started
Methods
- pipe() (aliases: add_pipe())
- send()
- set_container() (aliases: setContainer())
- then() (aliases: run())
- then_return() (aliases: run_and_return(), thenReturn())
- through() (aliases: pipes())
- via()

Installation

It's recommended that you install Pipeline as a project dependency via Composer:

composer require stellarwp/pipeline

We actually recommend that this library gets included in your project using Strauss.

Luckily, adding Strauss to your composer.json is only slightly more complicated than adding a typical dependency, so checkout our strauss docs.

An important note on namespaces:

The docs will in this repo all use StellarWP\Pipeline as the base namespace, however, if you are using Strauss to prefix namespaces in your project, you will need to adapt the namespaces accordingly. (Example: Boom\Shakalaka\StellarWP\Pipeline)

Prerequisites

There aren't any required prerequisites of note.

However! If you wish to use the container-based pipes, you will need a container that conforms to the ContainerInterface interface found in stellarwp/container-contract.

Getting started

Luckily, there isn't a whole lot to Pipelines from a code perspective, so implementing them is pretty easy. We'll walk through some of the basic concepts.

Important note: The examples provide a string as input data. That is just for simplicity's sake! You can actually pass whatever you want - a scalar, an object, an array, whatever.

Creating a simple pipeline

Let's say you have a string that you want to pass through a series of steps in order to manipulate it. You can create a pipeline to do that like so:

flowchart LR
	input[String]
	subgraph Pipeline
		pipe1[ucwords]
		pipe2[trim]

		pipe1 --> pipe2
	end
	output[Output data]

	input --> pipe1
	pipe2 --> output

use StellarWP\Pipeline\Pipeline;

// Create a new pipeline instance.
$pipeline = new Pipeline();

// Send a string through the pipeline.
$result = $pipeline->send( 'a sample string that is passed through to all pipes.' )
	->through(
		'ucwords',
		'trim'
	)->then_return();

// The output would be stored in $result and would be:
// A Sample String That Is Passed Through To All Pipes.
echo $result;

Building pipelines in parts

You don't need to build the pipeline all at once, you can spread it out over a number of lines.

flowchart LR
	input[String]
	subgraph Pipeline
		pipe1[ucwords]
		pipe2[trim]
		pipe3[strrev]

		pipe1 --> pipe2
		pipe2 --> pipe3
	end
	output[Output data]

	input --> pipe1
	pipe3 --> output

use StellarWP\Pipeline\Pipeline;

// Create a new pipeline instance.
$pipeline = new Pipeline();

// Declare the pipes that you want to run against the
// string in the order you want them to execute.
// The method `pipes()` is an alias of `through()`.
$pipeline->pipes(
	'ucwords',
	'trim'
);

// Add another pipe to the pipeline.
// The method `add_pipe()` is an alias of `pipe()`.
$pipeline->add_pipe( 'strrev' );

// Declare what you are sending through the pipeline.
$pipeline->send( 'potato    ' );

// Process the pipeline and get the result.
// The method `run()` is an alias of `then_return()`.
$result = $pipeline->run();

// The result will be: `otatoP`
echo $result;

Using closures

If you have a more complicated function that you wish to use as a pipe, you can pass in a callable instead of a string. Your closure will need to accept two parameters, the first being the input data and the second being the next item in the pipeline.

flowchart LR
	input[String]
	subgraph Pipeline
		pipe1[Closure]
		pipe2[ucwords]

		pipe1 --> pipe2
	end
	output[Output data]

	input --> pipe1
	pipe2 --> output

use StellarWP\Pipeline\Pipeline;

$pipeline  = new Pipeline();

$pipeline->pipes(
	static function ( $passable, Closure $next ) {
		$passable = str_ireplace( 'All', 'All The', $passable );

		return $next( $passable );
	},
	'ucwords'
);

$pipeline->send( 'a sample string that is passed through to all pipes.         ' );
$result = $pipeline->run();

// The output would be stored in $result and would be:
// A Sample String That Is Passed Through To All The Pipes.
echo $result;

Using classes with the `handle` method

You can even create your own classes to use as pipes in the pipeline. For a class to be usable in the pipeline, it needs a method that accepts two parameters, the first being the input data and the second being the next item in the pipeline.

By default, the Pipeline expects that the method is called handle. If you want to use that method name, you can optionally implement the StellarWP\Pipeline\Contracts\Pipe interface to enforce that method convention.

Example classes

First class:

use StellarWP\Pipeline\Contracts\Pipe;

class SweetUppercasePipe implements Pipe {
	public function handle( $passable, Closure $next ) {
		$passable = ucwords( $passable );

		return $next( $passable );
	}
}

Second class:

use StellarWP\Pipeline\Contracts\Pipe;

class TrimTheStringPipe implements Pipe {
	public function handle( $passable, Closure $next ) {
		$passable = trim( $passable );

		return $next( $passable );
	}
}

Example pipeline

flowchart LR
	input[String]
	subgraph Pipeline
		pipe1[SweetUppercasePipe::handle]
		pipe2[TrimTheStringPipe::handle]

		pipe1 --> pipe2
	end
	output[Output data]

	input --> pipe1
	pipe2 --> output

use StellarWP\Pipeline\Pipeline;

$pipeline = new Pipeline();

$pipeline->pipes(
	new SweetUppercasePipe(),
	new TrimTheStringPipe()
);

$pipeline->send( 'a sample string that is passed through to all pipes.         ' );
$result = $pipeline->run();

// The output would be stored in $result and would be:
// A Sample String That Is Passed Through To All Pipes.
echo $result;

Using classes with a custom method

If you want to use classes but want to use a different method than the expected default (handle), you can declare the alternate method name using the via() method.

Example classes

First class:

class DifferentSweetUppercasePipe {
	public function execute( $passable, Closure $next ) {
		$passable = ucwords( $passable );

		return $next( $passable );
	}
}

Second class:

class DifferentTrimTheStringPipe {
	public function execute( $passable, Closure $next ) {
		$passable = trime( $passable );

		return $next( $passable );
	}
}

Example pipeline

flowchart LR
	input[String]
	subgraph Pipeline
		pipe1[DifferentSweetUppercasePipe::execute]
		pipe2[DifferentTrimTheStringPipe::execute]

		pipe1 --> pipe2
	end
	output[Output data]

	input --> pipe1
	pipe2 --> output

use StellarWP\Pipeline\Pipeline;

$pipeline = new Pipeline();

// Set the method to use the `execute()` method instead of the default `handle()`.
$pipeline->via( 'execute' );

$pipeline->pipes(
	new DifferentSweetUppercasePipe(),
	new DifferentTrimTheStringPipe()
);

$pipeline->send( 'a sample string that is passed through to all pipes.         ' );
$result = $pipeline->run();

// The output would be stored in $result and would be:
// A Sample String That Is Passed Through To All Pipes.
echo $result;

Bailing early

Sometimes in the middle of a pipeline, you want to stop processing the rest of the pipes and return a value. Luckily, you can do this with a return statement!

Example pipeline

use StellarWP\Pipeline\Pipeline;

$pipeline  = new Pipeline();

$pipeline->pipes(
	'trim',
	static function ( $passable, Closure $next ) {
		if ( $passable === 'bork' ) {
			return $passable;
		}

		return $next( $passable );
	},
	'ucwords'
);

$pipeline->send( 'bork     ' );
$result = $pipeline->run();

// The output would be stored in $result and would be: "bork"
// It would not get to the `ucwords` pipe.
echo $result;

$pipeline->send( 'cowbell     ' );
$result = $pipeline->run();

// The output would be stored in $result and would be: "Cowbell" because it WOULD get to the `ucwords` pipe due to
// the second pipe only returning if the value is "bork".
echo $result;

Doing more than returning

Sometimes you may want to do more than returning the result when the pipeline completes. You can do that by using the then() (or its alias, run()) method instead of then_return().

Example pipeline

flowchart LR
	input[String]
	pipe3[Closure]
	subgraph Pipeline
		pipe1[ucwords]
		pipe2[trim]

		pipe1 --> pipe2
	end
	output[Output data]

	input --> pipe1
	pipe2 --> pipe3
	pipe3 --> output

use StellarWP\Pipeline\Pipeline;

// Create a new pipeline instance.
$pipeline = new Pipeline();

// Declare the pipes that you want to run against the
// string in the order you want them to execute.
// The method `pipes()` is an alias of `through()`.
$pipeline->pipes(
	'ucwords',
	'trim'
);

// Declare what you are sending through the pipeline.
$pipeline->send( 'a sample string that is passed through to all pipes.         ' );

// Process the pipeline and get the result.
$result = $pipeline->then( static function ( $passable ) {
	return str_ireplace( 'A Sample', 'A Nice Long', $passable );
} );

// The output would be stored in $result and would be:
// A Nice Long String That Is Passed Through To All Pipes.
echo $result;

Using a container in the pipeline

Pipelines can be instantiated with a container that conforms to the stellarwp/container-contract StellarWP\ContainerContract\ContainerInterface interface. Adding a container to the pipeline allows you to pass classes as pipes and allow those classes to be instantiated when the pipeline is being run.

flowchart LR
	input[String]
	subgraph Pipeline
		pipe1[SweetUppercasePipe::handle]
		pipe2[TrimTheStringPipe::handle]

		pipe1 --> pipe2
	end
	output[Output data]

	input --> pipe1
	pipe2 --> output

use StellarWP\Pipeline\Pipeline;
use MyProject\Container;

// Create a new container instance.
$container = new Container();
$pipeline  = new Pipeline( $container );

// Let's add some classes to the pipeline that we declared in a previous example.
$pipeline->pipes(
	SweetUppercasePipe::class,
	TrimTheStringPipe::class
);

$pipeline->send( 'a sample string that is passed through to all pipes.         ' );
$result = $pipeline->run();

// The output would be stored in $result and would be:
// A Sample String That Is Passed Through To All Pipes.
echo $result;

Declaring pipelines for reuse

A common approach to using pipelines is to declare them in a dependency injection container so that you can get an instance of a specifically configured pipeline when you need it.

Example

In this example, we are accepting in a WP_REST_Response object and we want to use a pipeline to process the response and fire off some actions based on the contents of the object.

We'll start with a couple of assumptions:

We are building some WordPress logic.
We will declare the reusable pipelines in a Service Provider class that extends a class named MyProject\AbstractServiceProvider and we can pretend that it accepts a container instance as a constructor argument.
That Service Provider class gets instantiated somewhere in our application and has a class property called $container that holds a container instance.
Our container conforms to the StellarWP\ContainerContract\ContainerInterface interface from the stellarwp/container-contract library.

This example's directory structure looks something like this:

MyProject/
	Listeners/
		Listener.php
	Providers/
		Service_Provider.php
	Response/
		Intake_Response.php
		Failed_Response.php
		Response_Transporter.php
	Container.php
	Put_It_All_Together.php

Service provider

First, we'll create our service provider class.

namespace MyProject\Providers;

use StellarWP\Pipeline\Pipeline;
use MyProject\Container;
use MyProject\Response\Intake_Response;
use MyProject\Response\Failed_Response;

class Service_Provider {
	/**
	 * @var string
	 */
	const REQUEST_PIPELINE = 'myproject.request-pipeline';

	/**
	 * @var ContainerInterface
	 */
	protected $container;

	/**
	 * @param ContainerInterface $container
	 */
	public function __construct( ContainerInterface $container ) {
		$this->container = $container;
	}

	/**
	* Register some services into the container.
	 */
	public function register() {
		// Bind `request-pipeline` to the container as a singleton. The first time that `->get( 'request-pipeline' )` is
		// called, the pipeline will will be instantiated and returned. Subsequent calls to `->get( 'request-pipeline' )`
		// will return the same instance of the pipeline.
		$this->container->singleton( self::REQUEST_PIPELINE, function(): Pipeline {
			$pipeline = new Pipeline( $this->container );
			$pipeline->pipes(
				Intake_Response::class,
				Failed_Response::class,
			);

			return $pipeline;
		} );

		// Bind the class name of Listener to the container. Any time that `->get( Listener::class )` is called, a new
		// instance of the Listener will be returned with the `request-pipeline` injected into the constructor.
		$this->container->bind( Listener::class, static function ( ContainerInterface $container ): Listener {
			return new Listener( $container->get( self::REQUEST_PIPELINE ) );
		} );
	}
}

Response_Transporter

Let's create a really simple object that will hold both a WP_REST_Request and a WP_REST_Response instance. This will be the object that we pass through our pipeline.

namespace MyProject\Response;

use WP_REST_Request;
use WP_REST_Response;

class Response_Transporter {
	/**
	 * @var WP_REST_Request
	 */
	public $request;

	/**
	 * @var WP_REST_Response
	 */
	public $response;

	/**
	 * @param WP_REST_Request $request
	 * @param WP_REST_Response $response
	 */
	public function __construct( WP_REST_Request $request, WP_REST_Response $response ) {
		$this->request  = $request;
		$this->response = $response;
	}
}

Intake_Response

Next, we'll create our Intake_Response class.

namespace MyProject\Response;

use StellarWP\Pipeline\Contracts\Pipe;
use WP_REST_Response;
use WP_Http;

class Intake_Response implements Pipe {
	public static $name = 'Response received';
	public static $endpoint = '/myproject/v1/borkborkbork';

	public function handle( Response_Transporter $transporter, Closure $next ): WP_REST_Response {
		// If the response is for the endpoint we're looking for, we'll process it.
		// Otherwise, it'll just keep moving through the pipeline.
		if ( $transporter->request->get_route() === static::$endpoint ) {
			$params = (array) $transporter->response->get_data();
			$status = $transporter->response->get_status();

			$data = [
				'status' => $status,
				'params' => $params,
			];

			/**
			 * Advertise that we've received the response and what its data is.
			 *
			 * @param string $name The name of the response.
			 * @param array  $data The data that was received.
			 */
			do_action( 'myproject/rest/event', static::$name, $data );
		}

		// Pass the transporter on to the next pipe in the pipeline.
		return $next( $transporter );
	}
}

Failed_Response

Next, we'll create our Failed_Response class.

namespace MyProject\Response;

use StellarWP\Pipeline\Contracts\Pipe;
use WP_REST_Response;

class Failed_Response implements Pipe {
	public static $name = 'Response failed';
	public static $endpoint = '/myproject/v1/borkborkbork';

	public function handle( Response_Transporter $transporter, Closure $next ): WP_REST_Response {
		// If the response is for the endpoint we're looking for, we'll process it.
		// Otherwise, it'll just keep moving through the pipeline.
		if ( $transporter->request->get_route() === static::$endpoint ) {
			$status  = $transporter->response->get_status();
			$success = $status >= WP_Http::OK && $status < WP_Http::BAD_REQUEST;

			// If the response was successful, let's keep moving through the pipeline.
			if ( $success ) {
				return $next( $transporter );
			}

			/**
			 * Oh no! The response was not successful. Let's notify our application that something went wrong.
			 *
			 * @param string $name The name of the response.
			 * @param array  $data The data associated with the error.
			 */
			do_action( 'myproject/rest/event', static::$name, [
				'error-params' => $transporter->response->get_data(),
			] );
		}

		// Pass the transporter on to the next pipe in the pipeline.
		return $next( $transporter );
	}
}

Listener

Finally, we'll create our Listener class.

namespace MyProject\Listeners;

use MyProject\Container;
use MyProject\Response\Response_Transporter;
use WP_REST_Request;
use WP_REST_Response;

class Listener {
	/**
	 * @var Pipeline
	 */
	protected $response_pipeline;

	/**
	 * @param Pipeline $response_pipeline
	 */
	public function __construct( Pipeline $response_pipeline ) {
		$this->response_pipeline = $response_pipeline;
	}

	/**
	 * @param WP_REST_Response $response The response that was received.
	 * @param WP_REST_Request  $request  The request that was made.
	 */
	public function handle_response( WP_REST_Response $response, WP_REST_Request $request ): void {
		$response = rest_ensure_response( $response );

		if ( is_wp_error( $response ) ) {
			$response = rest_convert_error_to_response( $response );
		}

		return $this->response_pipeline->send( new Response_Transporter( $request, $response ) )->then_return();
	}

Let's put it all together

namespace MyProject;

use MyProject\Container;
use MyProject\Listeners\Listener;
use MyProject\Providers\Service_Provider;

// Typically the next three lines would be done in a more application-relevant location, however, for the sake of
// this example, we'll just include them here.
$container = new Container();
$provider  = new Service_Provider( $container );
$provider->register();

// Likewise, these lines would likely be done in a class somewhere.
$request  = new WP_REST_Request( 'GET', '/myproject/v1/borkborkbork', [ 'color' => 'blue' ] );
$response = rest_do_request( $request );

// Get an instance of the Listener class.
$listener = $container->get( Listener::class );

// Pass the request to the listener, which will invoke the pipeline.
$listener->handle_response( $response, $request );

// If the request was successful, the `myproject/rest/event` action will be fired once to indicate
// that the response was received.

// If the request was NOT successful, the `myproject/rest/event` action will be fired once to indicate
// that the response was received. And a second time to indicate that there was an error.

// We can do the same thing for other requests.

// Likewise, these lines would likely be done in a class somewhere. These would probably live in different classes.
$request  = new WP_REST_Request( 'GET', '/myproject/v1/something-else' );
$response = rest_do_request( $request );
$listener = $container->get( Listener::class );
$listener->handle_response( $response, $request );

$request  = new WP_REST_Request( 'GET', 'myproject/v1/borkborkbork' );
$response = rest_do_request( $request );
$listener = $container->get( Listener::class );
$listener->handle_response( $response, $request );

Methods

`pipe()`

This method is used to add a pipe to the pipeline.

public function pipe( array|mixed $pipes ): self

Aliases: add_pipe()

Examples

$pipeline->pipe( 'ucwords' );
// or
$pipeline->add_pipe( 'ucwords' );
// or
$pipeline->pipe( [ 'ucwords', 'trim' ] );

`send()`

This method is used to set the object being passed through the pipeline.

public function send( mixed $passable ): self

Examples

// Send a scalar.
$pipeline->send( 'Some string' );

// Send an object.
$pipeline->send( $my_object );

`set_container()`

This method is used to set the container instance.

public function set_container( ContainerInterface $container ): self

Aliases: setContainer()

Examples

$pipeline->set_container( $container );

`then()`

This method is used to run the pipeline and return the result.

public function then( Closure $destination = null ): mixed

Aliases: run()

Examples

$pipeline->then();

// Use the alias.
$pipeline->run();

// Provide a function to run before returning the result.
$pipeline->then( 'trim' );

// Provide a closure to run before returning the result.
$pipeline->then( static function ( $passable ) {
	return trim( $passable );
} );

// Provide an object as a pipe to run before returning the result.
$pipeline->then( new TrimTheStringPipe() );

// Provide an class name as a pipe to run before returning the result.
$pipeline->then( TrimTheStringPipe::class );

`then_return()`

This method is used to run the pipeline and return the result.

public function then_return(): mixed

Aliases: run_and_return(), thenReturn()

Examples

$pipeline->then_return();
// Use an alias.
$pipeline->thenReturn();
// Use the other alias.
$pipeline->run_and_return();

`through()`

This method is used to set the handlers (or "pipes") that are used to process the data.

public function through( array|mixed $pipes ): self

Aliases: pipes()

Examples

// You can provide any number of pipes.
$pipeline->through( 'ucwords', 'trim' );

// Using the alias.
$pipeline->pipes( 'ucwords', 'trim' );

// Pass an array of pipes.
$pipeline->through( [ 'ucwords', 'trim' ] );

// Pass closures as pipes.
$pipeline->through( static function ( $passable, Closure $next ) {
	$passable = str_ireplace( 'All', 'All The', $passable );

	return $next( $passable );
} );

// Pass objects as pipes.
$pipeline->through( new SweetUppercasePipe(), new TrimTheStringPipe() );

// If you have a container, you can pass class names as pipes.
$pipeline->through( SweetUppercasePipe::class, TrimTheStringPipe::class );

`via()`

This method is used to set the method to call on all the pipes in the pipeline.

public function via( string $method ): self

Examples

// Set the method used in all classes in the pipeline to process the data as `execute()`.
$pipeline->via( 'execute' );

// Set the method used in all classes in the pipeline to process the data as `borkborkbork()`.
$pipeline->via( 'borkborkbork' );

stellarwp / pipeline

Maintainers

Details

README

Table of contents

Installation

Prerequisites

Getting started

Creating a simple pipeline

Building pipelines in parts

Using closures

Using classes with the handle method

Example classes

Example pipeline

Using classes with a custom method

Example classes

Example pipeline

Bailing early

Example pipeline

Doing more than returning

Example pipeline

Using a container in the pipeline

Declaring pipelines for reuse

Example

Service provider

Response_Transporter

Intake_Response

Failed_Response

Listener

Let's put it all together

Methods

pipe()

Examples

send()

Examples

set_container()

Examples

then()

Examples

then_return()

Examples

through()

Examples

via()

Examples

Using classes with the `handle` method

`pipe()`

`send()`

`set_container()`

`then()`

`then_return()`

`through()`

`via()`