Use a property

Author: Nyholm

README.md

@@ -81,20 +81,26 @@ class Pool implements CacheItemPoolInterface, TaggablePoolInterface
 
 ### Implement interface and use trait for CacheItemInterface
 
-The purpose of the trait is to be able to return a `taggedKey` and a normal `key`. Use the trait and rename your
-`getKey()` to `getTaggedKey()`. 
+The purpose of the trait is to be able to return a `taggedKey` and a normal `key`. The trait has one protected function 
+`getKeyFromTaggedKey()` and one public function `getTaggedkey()`. You should use the trait and make sure you set values
+to your two keys. 
 
 ```php
 class Pool implements CacheItemInterface, TaggableItemInterface
 {
   use TaggableItemTrait;
 
-  private $key;
+  private $normalKey;
 
-  // Rename from getKey to getTaggedKey
-  public function getTaggedKey() 
+  public function __construct($key)
   {
-    return $this->key;
+    $this->taggedKey = $key;
+    $this->normalKey = $this->getKeyFromTaggedKey($key);
+  }
+  
+  public function getKey() 
+  {
+    return $this->normalKey;
   }
 
   // ...

src/TaggableItemTrait.php

@@ -17,22 +17,31 @@
 trait TaggableItemTrait
 {
     /**
+     * @type string
+     */
+    protected $taggedKey;
+
+    /**
+     * A key that is dependent on the tags.
+     *
      * @return string
      */
-    abstract public function getTaggedKey();
+    public function getTaggedKey()
+    {
+        return $this->taggedKey;
+    }
 
     /**
-     * Return the key for this item.
+     * Return the cache key for this item. This is the generic cache key that the calling library sees.
      *
      * @return string
      */
-    public function getKey()
+    protected function getKeyFromTaggedKey($taggedKey)
     {
-        $key = $this->getTaggedKey();
-        if (false === $pos = strrpos($key, ':')) {
-            return $key;
+        if (false === $pos = strrpos($taggedKey, ':')) {
+            return $taggedKey;
         }
 
-        return substr($key, $pos + 1);
+        return substr($taggedKey, $pos + 1);
     }
 }

tests/Helper/CacheItem.php

@@ -39,7 +39,8 @@ class CacheItem implements CacheItemInterface, TaggableItemInterface
      */
     public function __construct($key)
     {
-        $this->key = $key;
+        $this->taggedKey = $key;
+        $this->key       = $this->getKeyFromTaggedKey($key);
     }
 
     /**
@@ -53,7 +54,7 @@ public function isHit()
     /**
      * @return string
      */
-    public function getTaggedKey()
+    public function getKey()
     {
         return $this->key;
     }