规格模式（Specification）

目的

构建一个清晰的业务规则规范，其中每条规则都能被针对性地检查。每个规范类中都有一个称为isSatisfiedBy的方法，方法判断给定的规则是否满足规范从而返回 true 或 false。

例子

UML Diagram

file

代码

你可以在 GitHub 中找到这段代码。

Item.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification;
  6. class Item
  7. {
  8.     /**
  9.      * @var float
  10.      */
  11.     private $price;
  13.     public function __construct(float $price)
  14.     {
  15.         $this->price = $price;
  16.     }
  18.     public function getPrice(): float
  19.     {
  20.         return $this->price;
  21.     }
  22. }

SpecificationInterface.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification;
  6. interface SpecificationInterface
  7. {
  8.     public function isSatisfiedBy(Item $item): bool;
  9. }

OrSpecification.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification;
  6. class OrSpecification implements SpecificationInterface
  7. {
  8.     /**
  9.      * @var SpecificationInterface[]
  10.      */
  11.     private $specifications;
  13.     /**
  14.      * @param SpecificationInterface[] ...$specifications
  15.      */
  16.     public function __construct(SpecificationInterface ...$specifications)
  17.     {
  18.         $this->specifications = $specifications;
  19.     }
  21.     /**
  22.      * 如果有一条规则符合条件，返回 true，否则返回 false
  23.      */
  24.     public function isSatisfiedBy(Item $item): bool
  25.     {
  26.         foreach ($this->specifications as $specification) {
  27.             if ($specification->isSatisfiedBy($item)) {
  28.                 return true;
  29.             }
  30.         }
  31.         return false;
  32.     }
  33. }

PriceSpecification.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification;
  6. class PriceSpecification implements SpecificationInterface
  7. {
  8.     /**
  9.      * @var float|null
  10.      */
  11.     private $maxPrice;
  13.     /**
  14.      * @var float|null
  15.      */
  16.     private $minPrice;
  18.     /**
  19.      * @param float $minPrice
  20.      * @param float $maxPrice
  21.      */
  22.     public function __construct($minPrice, $maxPrice)
  23.     {
  24.         $this->minPrice = $minPrice;
  25.         $this->maxPrice = $maxPrice;
  26.     }
  28.     public function isSatisfiedBy(Item $item): bool
  29.     {
  30.         if ($this->maxPrice !== null && $item->getPrice() > $this->maxPrice) {
  31.             return false;
  32.         }
  34.         if ($this->minPrice !== null && $item->getPrice() < $this->minPrice) {
  35.             return false;
  36.         }
  38.         return true;
  39.     }
  40. }

AndSpecification.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification;
  6. class AndSpecification implements SpecificationInterface
  7. {
  8.     /**
  9.      * @var SpecificationInterface[]
  10.      */
  11.     private $specifications;
  13.     /**
  14.      * @param SpecificationInterface[] ...$specifications
  15.      */
  16.     public function __construct(SpecificationInterface ...$specifications)
  17.     {
  18.         $this->specifications = $specifications;
  19.     }
  21.     /**
  22.      * 如果有一条规则不符合条件，返回 false，否则返回 true
  23.      */
  24.     public function isSatisfiedBy(Item $item): bool
  25.     {
  26.         foreach ($this->specifications as $specification) {
  27.             if (!$specification->isSatisfiedBy($item)) {
  28.                 return false;
  29.             }
  30.         }
  32.         return true;
  33.     }
  34. }

NotSpecification.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification;
  6. class NotSpecification implements SpecificationInterface
  7. {
  8.     /**
  9.      * @var SpecificationInterface
  10.      */
  11.     private $specification;
  13.     public function __construct(SpecificationInterface $specification)
  14.     {
  15.         $this->specification = $specification;
  16.     }
  18.     public function isSatisfiedBy(Item $item): bool
  19.     {
  20.         return !$this->specification->isSatisfiedBy($item);
  21.     }
  22. }

测试

Tests/SpecificationTest.php

  2. <?php
  4. namespace DesignPatterns\Behavioral\Specification\Tests;
  6. use DesignPatterns\Behavioral\Specification\Item;
  7. use DesignPatterns\Behavioral\Specification\NotSpecification;
  8. use DesignPatterns\Behavioral\Specification\OrSpecification;
  9. use DesignPatterns\Behavioral\Specification\AndSpecification;
  10. use DesignPatterns\Behavioral\Specification\PriceSpecification;
  11. use PHPUnit\Framework\TestCase;
  13. class SpecificationTest extends TestCase
  14. {
  15.     public function testCanOr()
  16.     {
  17.         $spec1 = new PriceSpecification(50, 99);
  18.         $spec2 = new PriceSpecification(101, 200);
  20.         $orSpec = new OrSpecification($spec1, $spec2);
  22.         $this->assertFalse($orSpec->isSatisfiedBy(new Item(100)));
  23.         $this->assertTrue($orSpec->isSatisfiedBy(new Item(51)));
  24.         $this->assertTrue($orSpec->isSatisfiedBy(new Item(150)));
  25.     }
  27.     public function testCanAnd()
  28.     {
  29.         $spec1 = new PriceSpecification(50, 100);
  30.         $spec2 = new PriceSpecification(80, 200);
  32.         $andSpec = new AndSpecification($spec1, $spec2);
  34.         $this->assertFalse($andSpec->isSatisfiedBy(new Item(150)));
  35.         $this->assertFalse($andSpec->isSatisfiedBy(new Item(1)));
  36.         $this->assertFalse($andSpec->isSatisfiedBy(new Item(51)));
  37.         $this->assertTrue($andSpec->isSatisfiedBy(new Item(100)));
  38.     }
  40.     public function testCanNot()
  41.     {
  42.         $spec1 = new PriceSpecification(50, 100);
  43.         $notSpec = new NotSpecification($spec1);
  45.         $this->assertTrue($notSpec->isSatisfiedBy(new Item(150)));
  46.         $this->assertFalse($notSpec->isSatisfiedBy(new Item(50)));
  47.     }
  48. }