introduced PostId and PostStatus and changed naming from Storage to Persistence

More/Repository/Domain/Post.php

@@ -5,10 +5,15 @@ namespace DesignPatterns\More\Repository\Domain;
 class Post
 {
     /**
-     * @var int
+     * @var PostId
      */
     private $id;
 
+    /**
+     * @var PostStatus
+     */
+    private $status;
+
     /**
      * @var string
      */
@@ -19,10 +24,11 @@ class Post
      */
     private $text;
 
-    public static function draft(int $id, string $title, string $text): Post
+    public static function draft(PostId $id, string $title, string $text): Post
     {
         return new self(
             $id,
+            PostStatus::fromString(PostStatus::STATE_DRAFT),
             $title,
             $text
         );
@@ -31,29 +37,37 @@ class Post
     public static function fromState(array $state): Post
     {
         return new self(
-            $state['id'],
+            PostId::fromInt($state['id']),
+            PostStatus::fromInt($state['statusId']),
             $state['title'],
             $state['text']
         );
     }
 
     /**
-     * @param int $id
-     * @param string $text
+     * @param PostId $id
+     * @param PostStatus $status
      * @param string $title
+     * @param string $text
      */
-    private function __construct(int $id, string $title, string $text)
+    private function __construct(PostId $id, PostStatus $status, string $title, string $text)
     {
         $this->id = $id;
+        $this->status = $status;
         $this->text = $text;
         $this->title = $title;
     }
 
-    public function getId(): int
+    public function getId(): PostId
     {
         return $this->id;
     }
 
+    public function getStatus(): PostStatus
+    {
+        return $this->status;
+    }
+
     public function getText(): string
     {
         return $this->text;

More/Repository/Domain/PostId.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace DesignPatterns\More\Repository\Domain;
+
+/**
+ * This is a perfect example of a value object that is identifiable by it's value alone and
+ * is guaranteed to be valid each time an instance is created. Another important property of value objects
+ * is immutability.
+ *
+ * Notice also the use of a named constructor (fromInt) which adds a little context when creating an instance.
+ */
+class PostId
+{
+    /**
+     * @var int
+     */
+    private $id;
+
+    public static function fromInt(int $id)
+    {
+        self::ensureIsValid($id);
+
+        return new self($id);
+    }
+
+    private function __construct(int $id)
+    {
+        $this->id = $id;
+    }
+
+    public function toInt(): int
+    {
+        return $this->id;
+    }
+
+    private static function ensureIsValid(int $id)
+    {
+        if ($id <= 0) {
+            throw new \InvalidArgumentException('Invalid PostId given');
+        }
+    }
+}

More/Repository/Domain/PostStatus.php

@@ -0,0 +1,80 @@
+<?php
+
+namespace DesignPatterns\More\Repository\Domain;
+
+/**
+ * Like PostId, this is a value object which holds the value of the current status of a Post. It can be constructed
+ * either from a string or int and is able to validate itself. An instance can then be converted back to int or string.
+ */
+class PostStatus
+{
+    const STATE_DRAFT_ID = 1;
+    const STATE_PUBLISHED_ID = 2;
+
+    const STATE_DRAFT = 'draft';
+    const STATE_PUBLISHED = 'published';
+
+    private static $validStates = [
+        self::STATE_DRAFT_ID => self::STATE_DRAFT,
+        self::STATE_PUBLISHED_ID => self::STATE_PUBLISHED,
+    ];
+
+    /**
+     * @var int
+     */
+    private $id;
+
+    /**
+     * @var string
+     */
+    private $name;
+
+    public static function fromInt(int $statusId)
+    {
+        self::ensureIsValidId($statusId);
+
+        return new self($statusId, self::$validStates[$statusId]);
+    }
+
+    public static function fromString(string $status)
+    {
+        self::ensureIsValidName($status);
+
+        return new self(array_search($status, self::$validStates), $status);
+    }
+
+    private function __construct(int $id, string $name)
+    {
+        $this->id = $id;
+        $this->name = $name;
+    }
+
+    public function toInt(): int
+    {
+        return $this->id;
+    }
+
+    /**
+     * there is a reason that I avoid using __toString() as it operates outside of the stack in PHP
+     * and is therefor not able to operate well with exceptions
+     */
+    public function toString(): string
+    {
+        return $this->name;
+    }
+
+    private static function ensureIsValidId(int $status)
+    {
+        if (!in_array($status, array_keys(self::$validStates), true)) {
+            throw new \InvalidArgumentException('Invalid status id given');
+        }
+    }
+
+
+    private static function ensureIsValidName(string $status)
+    {
+        if (!in_array($status, self::$validStates, true)) {
+            throw new \InvalidArgumentException('Invalid status name given');
+        }
+    }
+}