CMSEditLink method modified to support DataObject links and Example o…

…f using ElemenatalArea with DataObject

docs/en/examples/using_elementalArea_with_dataObject.md

@@ -0,0 +1,245 @@
+---
+title: Using ElementalArea with DataObject
+summary: Learn how to add ElementalArea to your models and manage it in ModalAdmin
+---
+
+# Using ElementalArea with DataObject
+
+## Creaating Model and adding ElementalArea
+
+In this example the class BlogPost will be created, it will extend DataObject class. Also new BlogPost Admin section will be created in Admin panel where CMS user can manage the BlogPosts. 
+
+Let's look at an example:
+
+**app/src/Admins/BlogPostsAdmin.php**
+
+```php
+namespace App\Admins;
+
+use App\Models\BlogPost;
+use SilverStripe\Admin\ModelAdmin;
+
+class BlogPostsAdmin extends ModelAdmin
+{
+
+    private static string $url_segment = 'blog-posts-admin';
+
+    private static string $menu_title = 'Blog Posts';
+
+    private static string $menu_icon_class = 'font-icon-block-banner';
+
+    private static array $managed_models = [
+        BlogPost::class,
+    ];
+}
+```
+
+``` $managed_models ``` - this static variable connects BlogPostAdmin with BlogPost, which will be created in the following code.
+When you create DataObject you should define connection between your DataObject and ElementalArea by adding ```$has_one``` relationship.
+In this example BlogPost will have one ElementalArea.
+
+**app/src/Models/BlogPost.php**
+
+```php
+
+namespace App\Models;
+
+use App\Admins\BlogPostsAdmin;
+
+class BlogPost extends DataObject
+{
+
+    private static string $table_name = 'BlogPost';
+
+    private static array $db = [
+        'Title' => 'Varchar(255)',
+        'Content' => 'HTMLText',
+    ]
+
+    private static $has_one = [
+        'ElementalArea' => ElementalArea::class,
+    ];
+
+    ...
+}
+ ```
+
+If you are using ElementalArea together with DataObject, it is important to define a few following methods in the class.
+First of all, CMSEditLink() method should be defined to generate link for opening editing section of the partucular BlogPost. 
+BaseElement uses link, that was created in CMSEditLink() method in BlogPost class, to generate new links for opening editing section of the particular Element.
+
+```php
+...
+
+class BlogPost extends DataObject
+{
+    ...
+
+    public function CMSEditLink()
+    {
+        // In this example we use BlogPostsAdmin class as Controller
+        $admin = BlogPostsAdmin::singleton();
+
+        // Makes link more readable. Instead App\Models\ BlogPost, we get App-Models-BlogPost
+        $sanitisedClassname = str_replace('\\', '-', $this->ClassName);
+
+        // Returns link to editing section with elements
+        return Controller::join_links(
+            $admin->Link($sanitisedClassname),
+            'EditForm/field/',
+            $sanitisedClassname,
+            'item',
+            $this->ID,
+        );
+    }
+
+    ...
+
+}
+
+```
+
+Method Link() doesn't exist in DataObject class, so you should define this method in your class. Since PreviewLink() method of BaseElement uses Link() method to generate Preview window in the BlogPost Admin section. You should add canArchive() method in your class as well to set rules for canDalete() method.
+You should also define AbsoluteLink() method for opening the tabs in the Elements.
+Use following code as an example to how simply create these methods.
+
+```php
+...
+
+class BlogPost extends DataObject
+{
+    ...
+
+    public function Link($action = null)
+    {
+        $admin = BlogPostsAdmin::singleton();
+
+        return $this->ID
+            ? Controller::join_links(
+                $admin->Link(str_replace('\\', '-', $this->ClassName)),
+                $this->ID
+                )
+            : null;
+    }
+
+    public function canArchive($member = null)
+    {
+        return $this->canDelete($member);
+    }
+
+    public function AbsoluteLink($action = null)
+    {
+        return null;
+    }
+}
+
+```
+
+Add ElementalAreasExtension to the DataObject
+
+**app/_config/elemental.yml**
+
+```yml
+
+App\Models\BlogPost:
+  extensions: 
+    - DNADesign\Elemental\Extensions\ElementalAreasExtension
+
+```
+
+## Creating Previewable DataObject in CMS admin section
+
+Class BlogPost can implement CMSPreviewable interface to show a preview.
+By making a following changes, you can append Preview window in the BlogPost Admin section
+
+**app/src/Admins/BlogPostsAdmin.php**
+
+```php
+...
+
+class BlogPostsAdmin extends ModelAdmin
+{
+    ...
+
+    private static $allowed_actions = [
+        'cmsPreview',
+    ];
+
+    private static $url_handlers = [
+        '$ModelClass/cmsPreview/$ID' => 'cmsPreview',
+    ];
+
+    public function cmsPreview()
+    {
+        $id = $this->urlParams['ID'];
+        $obj = $this->modelClass::get_by_id($id);
+        if (!$obj || !$obj->exists()) {
+            return $this->httpError(404);
+        }
+
+        // Include use of a front-end theme temporarily.
+        $oldThemes = SSViewer::get_themes();
+        SSViewer::set_themes(SSViewer::config()->get('themes'));
+        $preview = $obj->forTemplate();
+
+        // Make sure to set back to backend themes.
+        SSViewer::set_themes($oldThemes);
+
+        return $preview;
+    }
+
+}
+
+```
+
+**app/src/Models/BlogPost.php**
+
+```php
+...
+
+class BlogPost extends DataObject implements CMSPreviewable
+{
+    ...
+
+    public function PreviewLink($action = null)
+    {
+        $admin = BlogPostsAdmin::singleton();
+        return $this->ID
+            ? Controller::join_links(
+                $admin->Link(str_replace('\\', '-', $this->ClassName)),
+                'cmsPreview',
+                $this->ID
+                )
+            : null;
+    }
+
+    // The following methods are required to show data in template
+
+    public function getMimeType()
+    {
+        return 'text/html';
+    }
+
+    public function forTemplate($holder = true)
+    {
+        return $this->renderWith(['type' => 'Blogs', self::class]);
+    }
+}
+
+```
+Add template for DataObject to display data. In this example we create BlogPost.ss file in templates/App/Models/Blogs directory.
+
+**BlogPost.ss**
+
+```yml
+
+<% if $ElementalArea %>
+    $ElementalArea
+<% end_if %>
+
+```
+
+
+## Related Documentation
+
+* [Preview](/developer_guides/customising_the_admin_interface/preview/)

src/Models/BaseElement.php

@@ -721,21 +721,38 @@ public function CMSEditLink($directLink = false)
             return $link;
         }
 
-        if (!$page instanceof SiteTree && method_exists($page, 'CMSEditLink')) {
-            $link = Controller::join_links($page->CMSEditLink(), 'ItemEditForm');
+        if (!$page instanceof SiteTree) {
+            if (ClassInfo::hasMethod($page, 'CMSEditLink')) {
+                $link = Controller::join_links($page->CMSEditLink(), 'ItemEditForm');
+            } else {
+                $link = null;
+                $this->extend('updateCMSEditLink', $link);
+                return $link;
+            }
         } else {
             $link = $page->CMSEditLink();
         }
 
         // In-line editable blocks should just take you to the page. Editable ones should add the suffix for detail form
         if (!$this->inlineEditable() || $directLink) {
-            $link = Controller::join_links(
-                singleton(CMSPageEditController::class)->Link('EditForm'),
-                $page->ID,
-                'field/' . $relationName . '/item/',
-                $this->ID,
-                'edit'
-            );
+            if (!$page instanceof SiteTree) {
+                $link = Controller::join_links(
+                    $link,
+                    'field',
+                    $relationName,
+                    'item',
+                    $this->ID,
+                    'edit'
+                );
+            } else {
+                $link = Controller::join_links(
+                    singleton(CMSPageEditController::class)->Link('EditForm'),
+                    $page->ID,
+                    'field/' . $relationName . '/item/',
+                    $this->ID,
+                    'edit'
+                );
+            }
         }
 
         $this->extend('updateCMSEditLink', $link);