CODESAMPLE

Specification - PHP

Specification PHP

The Specification pattern is a behavioral design pattern that defines a way to represent complex conditions using boolean expressions. It allows you to decouple the logic that determines if something is valid from the object it’s being applied to. This promotes reusability and composability of validation rules.

The code defines an Item class and a Specification interface with a isSatisfiedBy() method. Concrete specifications like PriceSpecification and NameSpecification implement this interface to check specific item properties. These specifications can be combined using logical operators (and, or, not) to create more complex rules. The example demonstrates checking if an item is both expensive and has a valid name. This approach is idiomatic PHP due to its flexible type system and support for interfaces and object composition.

<?php

interface Specification
{
    public function isSatisfiedBy(Item $item): bool;
}

class Item
{
    public function __construct(
        public string $name,
        public float $price
    ) {}
}

class PriceSpecification implements Specification
{
    public function __construct(public float $minPrice) {}

    public function isSatisfiedBy(Item $item): bool
    {
        return $item->price >= $this->minPrice;
    }
}

class NameSpecification implements Specification
{
    public function isSatisfiedBy(Item $item): bool
    {
        return !empty($item->name);
    }
}

class AndSpecification implements Specification
{
    public function __construct(
        private Specification $specification1,
        private Specification $specification2
    ) {}

    public function isSatisfiedBy(Item $item): bool
    {
        return $this->specification1->isSatisfiedBy($item) && $this->specification2->isSatisfiedBy($item);
    }
}

// Usage
$item1 = new Item("Laptop", 1200.00);
$item2 = new Item("", 500.00);

$expensive = new PriceSpecification(1000.00);
$validName = new NameSpecification();

$combinedSpec = new AndSpecification($expensive, $validName);

if ($combinedSpec->isSatisfiedBy($item1)) {
    echo "Item 1 is expensive and has a valid name.\n";
} else {
    echo "Item 1 does not meet the criteria.\n";
}

if ($combinedSpec->isSatisfiedBy($item2)) {
    echo "Item 2 is expensive and has a valid name.\n";
} else {
    echo "Item 2 does not meet the criteria.\n";
}

?>