Update 8. Demonstrate the ability to manage the cache.md

Author: simpleadm

1. Magento Architecture and Customization Techniques/8. Demonstrate the ability to manage the cache.md

@@ -113,11 +113,45 @@ How would you clean the cache? In which case would you refresh cache/flash cache
 
 ### Describe how to clear the cache programmatically.
 
-What mechanisms are available for clearing all or part of the cache?
+To clear the cache programmatically you neeed to call next the methods:
+- [\Magento\Framework\App\CacheInterface::remove($identifier)](https://github.com/magento/magento2/blob/2.2-develop/lib/internal/Magento/Framework/App/CacheInterface.php#L48) - remove cached data by identifier
+- [\Magento\Framework\App\CacheInterface::clean($tags = [])](https://github.com/magento/magento2/blob/2.2-develop/lib/internal/Magento/Framework/App/CacheInterface.php#L56) - clean cached data by specific tag
+
+##### What mechanisms are available for clearing all or part of the cache?
+
+Dispatch a `clean_cache_by_tags` event with parameter of the object you want to clear from the cache.
+
+Example: [\Magento\Framework\Model\AbstractModel](https://github.com/magento/magento2/blob/2.2-develop/lib/internal/Magento/Framework/Model/AbstractModel.php#L817) (afterSave, afterDelete methods)
+
+```php
+<?php
+public function afterSave()
+{
+    $this->cleanModelCache();
+    $this->_eventManager->dispatch('model_save_after', ['object' => $this]);
+    $this->_eventManager->dispatch('clean_cache_by_tags', ['object' => $this]);
+    $this->_eventManager->dispatch($this->_eventPrefix . '_save_after', $this->_getEventData());
+    $this->updateStoredData();
+    return $this;
+}
+
+public function cleanModelCache()
+{
+    $tags = $this->getCacheTags();
+    if ($tags !== false) {
+        $this->_cacheManager->clean($tags); // \Magento\Framework\App\CacheInterface
+    }
+    return $this;
+}
+```
 
+Default `clean_cache_by_tags` event observers are: 
+- [Magento\PageCache\Observer\FlushCacheByTags](https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/PageCache/Observer/FlushCacheByTags.php#L57) - if Built-In caching is enabled 
+- [Magento\CacheInvalidate\Observer\InvalidateVarnishObserver](https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/CacheInvalidate/Observer/InvalidateVarnishObserver.php#L50)- if Varnish caching is enabled
 
 ###### Links
 - [Magento DevDocs - Magento cache overview](https://devdocs.magento.com/guides/v2.2/frontend-dev-guide/cache_for_frontdevs.html)
 - [Magento DevDocs - Configure caching](https://devdocs.magento.com/guides/v2.2/config-guide/cache.html)
 - [Magento DevDocs - Partial caching](https://devdocs.magento.com/guides/v2.2/extension-dev-guide/cache/partial-caching.html)
 - [Magento DevDocs - Full Page caching](https://devdocs.magento.com/guides/v2.2/extension-dev-guide/cache/page-caching.html)
+- [Magento DevDocs - Private content](https://devdocs.magento.com/guides/v2.2/extension-dev-guide/cache/page-caching/private-content.html)