About the analysis of PHP pipeline plug-in League\Pipeline

This article mainly introduces the analysis of the PHP pipeline plug-in League\Pipeline, which has certain reference value. Now I share it with you. Friends in need can refer to it

Pipeline design pattern

The water pipe is too long, and if one part is broken, it will leak, and it is not conducive to bending and turning in complex environments. Therefore, we will divide the water pipes into very short pipes, and then maximize the size of the pipes to have different functions, adapt to local conditions, and assemble them together to meet a variety of different needs.

This leads to the design pattern of Pipeline, which is to cut complex and lengthy processes into small processes and tasks. Each minimally quantified task can be reused to form complex and diverse processes by assembling different small tasks.

Finally, introduce the "input" into the pipeline, operate (process, filter) the input according to each small task, and finally output the results that meet the needs.

Today I mainly study "Pipeline", and by the way, I recommend a PHP plug-in: league/pipeline.

gulp

The first time I learned about the concept of "pipe" came from the use of gulp.

gulp is an automatic task runner based on NodeJS. She can automatically complete Javascript, Test, check, merge, compress, format, automatically refresh the browser, generate deployment files for sass, less and other files, and monitor the files to repeat the specified steps after changes. In terms of implementation, she draws on the pipe idea of ​​the Unix operating system. The output of the previous level directly becomes the input of the next level, making the operation very simple.

var gulp = require('gulp');
var less = require('gulp-less');
var minifyCSS = require('gulp-csso');
var concat = require('gulp-concat');
var sourcemaps = require('gulp-sourcemaps');

gulp.task('css', function(){
  return gulp.src('client/templates/*.less')
    .pipe(less())
    .pipe(minifyCSS())
    .pipe(gulp.dest('build/css'))
});

gulp.task('js', function(){
  return gulp.src('client/javascript/*.js')
    .pipe(sourcemaps.init())
    .pipe(concat('app.min.js'))
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('build/js'))
});

gulp.task('default', [ 'html', 'css', 'js' ]);

The above two task are mainly to parse, compress, output and other process operations on less and all js files, and then save them. to the corresponding folder; the output of each step is the input of the next step, just like the flow of water in a pipe.

IlluminatePipeline

The middleware in the Laravel framework is implemented using Illuminate\Pipeline. I originally wanted to write about my interpretation of the source code of "Laravel Middleware". But I found that there are already many posts on the Internet that explain it, so this article will briefly talk about how to use Illuminate\Pipeline.

Write a demo

public function demo(Request $request)
{
    $pipe1 = function ($payload, Closure $next) {
        $payload = $payload + 1;
        return $next($payload);
    };

    $pipe2 = function ($payload, Closure $next) {
        $payload = $payload * 3;
        return $next($payload);
    };

    $data = $request->input('data', 0);

    $pipeline = new Pipeline();

    return $pipeline
        ->send($data)
        ->through([$pipe1, $pipe2])
        ->then(function ($data) {
            return $data;
        });
}

##For For analysis of the source code, you can recommend reading this article. The analysis is quite thorough:

Implementation of Laravel Pipeline component https://www.insp.top/article/realization-of-pipeline-component-for -laravel

LeaguePipeline

The above simple use of

gulp and Illuminate\Pipeline just tells us that "Pipeline" is widely used. If we were asked to write a similar plug-in ourselves, I think it wouldn't be difficult.

Let me take the

League\Pipeline plug-in and take a look at its source code to see how it is implemented.

Brief description

This package provides a plug and play implementation of the Pipeline Pattern. It's an architectural pattern which encapsulates sequential processes. When used, it allows you to mix and match operation, and pipelines, to create new execution chains. The pipeline pattern is often compared to a production line, where each stage performs a certain operation on a given payload/subject. Stages can act on, manipulate, decorate, or even replace the payload.

If you find yourself passing results from one function to another to complete a series of tasks on a given subject, you might want to convert it into a pipeline.

https://pipeline. thephpleague.com/

Install plug-in

composer require league/pipeline

Write a demo

use League\Pipeline\Pipeline;

// 创建两个闭包函数
$pipe1 = function ($payload) {
    return $payload + 1;
};

$pipe2 = function ($payload) {
    return $payload * 3;
};

$route->map(
    'GET',
    '/demo',
    function (ServerRequestInterface $request, ResponseInterface $response
    ) use ($service, $pipe1, $pipe2) {
        $params = $request->getQueryParams();

        // 正常使用
        $pipeline1 = (new Pipeline)
            ->pipe($pipe1)
            ->pipe($pipe2);

        $callback1 = $pipeline1->process($params['data']);

        $response->getBody()->write("<h1 id="正常使用">正常使用</h1>");
        $response->getBody()->write("<p>结果：$callback1</p>");

        // 使用魔术方法
        $pipeline2 = (new Pipeline())
            ->pipe($pipe1)
            ->pipe($pipe2);

        $callback2 = $pipeline2($params['data']);

        $response->getBody()->write("<h1 id="使用魔术方法">使用魔术方法</h1>");
        $response->getBody()->write("<p>结果：$callback2</p>");

        // 使用 Builder
        $builder = new PipelineBuilder();
        $pipeline3 = $builder
            ->add($pipe1)
            ->add($pipe2)
            ->build();

        $callback3 = $pipeline3($params['data']);

        $response->getBody()->write("<h1 id="使用-Builder">使用 Builder</h1>");
        $response->getBody()->write("<p>结果：$callback3</p>");
        return $response;
    }
);

Run result

Interpretation of the source code

The entire plug-in only has these files:

PipelineInterface

<?php declare(strict_types=1);

namespace League\Pipeline;

interface PipelineInterface extends StageInterface
{
    /**
     * Create a new pipeline with an appended stage.
     *
     * @return static
     */
    public function pipe(callable $operation): PipelineInterface;
}

interface StageInterface
{
    /**
     * Process the payload.
     *
     * @param mixed $payload
     *
     * @return mixed
     */
    public function __invoke($payload);
}

This interface mainly uses the idea of ​​​​chain programming to continuously add pipes "pipe", and then adds a magic Method to run the passed parameters.

Let’s take a look at the function of this magic method:

mixed __invoke ([ $... ] )
当尝试以调用函数的方式调用一个对象时，__invoke() 方法会被自动调用。

如：

<?php class CallableClass 
{
    function __invoke($x) {
        var_dump($x);
    }
}
$obj = new CallableClass;
$obj(5);
var_dump(is_callable($obj));
?>

返回结果：

int(5)
bool(true)

Pipeline

<?php declare(strict_types=1);

namespace League\Pipeline;

class Pipeline implements PipelineInterface
{
    /**
     * @var callable[]
     */
    private $stages = [];

    /**
     * @var ProcessorInterface
     */
    private $processor;

    public function __construct(ProcessorInterface $processor = null, callable ...$stages)
    {
        $this->processor = $processor ?? new FingersCrossedProcessor;
        $this->stages = $stages;
    }

    public function pipe(callable $stage): PipelineInterface
    {
        $pipeline = clone $this;
        $pipeline->stages[] = $stage;

        return $pipeline;
    }

    public function process($payload)
    {
        return $this->processor->process($payload, ...$this->stages);
    }

    public function __invoke($payload)
    {
        return $this->process($payload);
    }
}

其中核心类 Pipeline 的作用主要就是两个：

1. 添加组装各个管道「pipe」；

2. 组装后，引水流动，执行 process($payload)，输出结果。

Processor

接好各种管道后，那就要「引水入渠」了。该插件提供了两个基础执行类，比较简单，直接看代码就能懂。

// 按照 $stages 数组顺利，遍历执行管道方法，再将结果传入下一个管道，让「水」一层层「流动」起来
class FingersCrossedProcessor implements ProcessorInterface
{
    public function process($payload, callable ...$stages)
    {
        foreach ($stages as $stage) {
            $payload = $stage($payload);
        }

        return $payload;
    }
}

// 增加一个额外的「过滤网」，经过每个管道后的结果，都需要 check，一旦满足则终止，直接输出结果。
class InterruptibleProcessor implements ProcessorInterface
{
    /**
     * @var callable
     */
    private $check;

    public function __construct(callable $check)
    {
        $this->check = $check;
    }

    public function process($payload, callable ...$stages)
    {
        $check = $this->check;

        foreach ($stages as $stage) {
            $payload = $stage($payload);

            if (true !== $check($payload)) {
                return $payload;
            }
        }

        return $payload;
    }
}

interface ProcessorInterface
{
    /**
     * Process the payload using multiple stages.
     *
     * @param mixed $payload
     *
     * @return mixed
     */
    public function process($payload, callable ...$stages);
}

我们完全也可以利用该接口，实现我们的方法来组装管道和「过滤网」。

PipelineBuilder

最后提供了一个 Builder，这个也很好理解：

class PipelineBuilder implements PipelineBuilderInterface
{
    /**
     * @var callable[]
     */
    private $stages = [];

    /**
     * @return self
     */
    public function add(callable $stage): PipelineBuilderInterface
    {
        $this->stages[] = $stage;

        return $this;
    }

    public function build(ProcessorInterface $processor = null): PipelineInterface
    {
        return new Pipeline($processor, ...$this->stages);
    }
}

interface PipelineBuilderInterface
{
    /**
     * Add an stage.
     *
     * @return self
     */
    public function add(callable $stage): PipelineBuilderInterface;

    /**
     * Build a new Pipeline object.
     */
    public function build(ProcessorInterface $processor = null): PipelineInterface;
}

总结

无论是对不同技术的横向理解，还是基于 Laravel 或者某些开源插件，我们都能学习到技术之上的通用原理和方法。再将这些原理和方法反作用于我们的实际代码开发中。

最近闲来没事，自己参考 Laravel 去写个简易框架，也将League\Pipeline 引入到框架中使用。

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