Specification pattern for Laravel

Implementation of the Specification pattern in PHP

Requirements

• PHP 8.1+

Installation

You can install the package via composer:

$ composer require kaivladimirv/laravel-specification-pattern

Usage

You can create a specification using the artisan command:

$ php artisan make:specification GreaterThanSpecification

This command will create a specification class in the App\Specifications namespace.

<?php

declare(strict_types=1);

namespace App\Specifications;

use Kaivladimirv\LaravelSpecificationPattern\AbstractSpecification

class GreaterThanSpecification extends AbstractSpecification
{
    protected function defineMessage(): string
    {
        // TODO: Implement defineMessage() method.    
    }

    protected function executeCheckIsSatisfiedBy(mixed $candidate): bool
    {
        return false;
    }
}

Adding business logic to the created specification:

<?php

declare(strict_types=1);

namespace App\Specifications;

use Kaivladimirv\LaravelSpecificationPattern\AbstractSpecification

class GreaterThanSpecification extends AbstractSpecification
{
+    public function __construct(readonly private int|float $number)
+    {
+    }
+    
    protected function defineMessage(): string
    {
-        // TODO: Implement defineMessage() method.
+        return "Number must be greater than $this->number";    
    }

    protected function executeCheckIsSatisfiedBy(mixed $candidate): bool
    {
-        return false;
+        return $candidate > $this->number;
    }
}

After adding business logic, you can use the specification by calling the isSatisfiedBy or throwExceptionIfIsNotSatisfiedBy methods.

Using the isSatisfiedBy method:

$greaterThan100Spec = new GreaterThanSpecification(100);

$greaterThan100Spec->isSatisfiedBy(200); // true
$greaterThan100Spec->isSatisfiedBy(99); // false

Using the throwExceptionIfIsNotSatisfiedBy method:

$greaterThan100Spec = new GreaterThanSpecification(100);

$greaterThan100Spec->throwExceptionIfIsNotSatisfiedBy(200); // No exception will be thrown here
$greaterThan100Spec->isSatisfiedBy(99); // An DomainException will be thrown here with the message "Number must be greater than 100"

You can change the exception type in the getExceptionClass method:

<?php

declare(strict_types=1);

namespace App\Specifications;

use Kaivladimirv\LaravelSpecificationPattern\AbstractSpecification

class GreaterThanSpecification extends AbstractSpecification
{
    public function __construct(readonly private int|float $number)
    {
    }
    
    protected function defineMessage(): string
    {
        return "Number must be greater than $this->number";    
    }

    protected function executeCheckIsSatisfiedBy(mixed $candidate): bool
    {
        return $candidate > $this->number;
    }
+    
+    protected function getExceptionClass(): string
+    {
+        return MyException::class;
+    }
}

License

The Task manager project is licensed for use under the MIT License (MIT). Please see LICENSE for more information.