DOC Updated Nested GridField docs

docs/en/index.md

@@ -159,39 +159,264 @@ Nested GridFields
 The `GridFieldNestedForm` component allows you to nest GridFields in the UI. It can be used with `DataObject` subclasses
 with the `Hierarchy` extension, or by specifying the relation used for nesting.
 
+Here is a small example of basic use of Nested GridField.
+
 ```php
-// Basic usage, defaults to the Children-method for Hierarchy objects.
-$grid->getConfig()->addComponent(GridFieldNestedForm::create());
+namespace App\Admin;
+
+use MyObject;
+use SilverStripe\Admin\ModelAdmin;
+use Symbiote\GridFieldExtensions\GridFieldNestedForm;
+
+class MyAdmin extends ModelAdmin
+{
+    //...
 
-// Usage with custom relation
-$grid->getConfig()->addComponent(GridFieldNestedForm::create()->setRelationName('MyRelation'));
+    public function getEditForm($id = null, $fields = null)
+    {
+        $form = parent::getEditForm($id, $fields);
+
+        $grid = $form->Fields()->dataFieldByName(MyObject::class);
+        // Add Nested GridField to main GridField
+        $grid->getConfig()->addComponent(GridFieldNestedForm::create());
+
+        return $form;
+    }
+}
 ```
 
-You can define your own custom GridField config for the nested GridField configuration by implementing a `getNestedConfig`
-on your nested model (should return a `GridField_Config` object).
+There are several ways to use Nested GridField. The implementation depends on the type of data you will be using in your GridField.
+For instance, if there is a `DataObject` that has the [`Hierarchy`](api:SilverStripe\ORM\Hierarchy\Hierarchy) extension, you can use the following approach.
+
+As an example, here we can use a typical hierarchy of the `Group` model, where another `Group` can serve as a parent.
+
 ```php
-class NestedObject extends DataObject
+namespace App\Extensions;
+
+use SilverStripe\Core\Extension;
+use SilverStripe\Security\Group;
+use Symbiote\GridFieldExtensions\GridFieldNestedForm;
+
+class MySecurityAdminExtension extends Extension
 {
-	private static $has_one = [
-		'Parent' => ParentObject::class
-	];
-
-	public function getNestedConfig(): GridFieldConfig
-	{
-		$config = new GridFieldConfig_RecordViewer();
-		return $config;
-	}
+    public function updateGridFieldConfig($config)
+    {
+        if ($this->owner->getModelClass() === Group::class) {
+            $config->addComponent(GridFieldNestedForm::create());
+        }
+    }
 }
 ```
 
-You can also modify the default config (a `GridFieldConfig_RecordEditor`) via an extension to the nested model class, by implementing
-`updateNestedConfig`, which will get the config object as the first parameter.
+Or also view a list of all members of a given group. Notice we call `setRelationName()` to explicitly state the relation which should be displayed in the Nested GridField.
+
 ```php
-class NestedObjectExtension extends DataExtension
+namespace App\Extensions;
+
+use SilverStripe\Core\Extension;
+use SilverStripe\Security\Group;
+use Symbiote\GridFieldExtensions\GridFieldNestedForm;
+
+class MySecurityAdminExtension extends Extension
 {
-	public function updateNestedConfig(GridFieldConfig &$config)
-	{
-		$config->removeComponentsByType(GridFieldPaginator::class);
-	}
+    public function updateGridFieldConfig($config)
+    {
+        if ($this->owner->getModelClass() === Group::class) {
+            $config->addComponent(GridFieldNestedForm::create()->setRelationName('Members'));
+        }
+    }
+}
+```
+
+```yml
+SilverStripe\Admin\SecurityAdmin:
+extensions:
+    - App\Extensions\MySecurityAdminExtension
+```
+
+Another way to use Nested GridField together with `DataObjects` that do not have the `Hierarchy` extension but have `has_many` relationships with other objects.
+Let's say you have the following `DataObject` that has multiple levels of relationships, and an admin section where the data of this object will be displayed.
+You want the user to be able to view information regarding this object and all nested objects on the same page, without the need to navigate to each object individually.
+In this case, you can use the following approach.
+
+```php
+namespace App\Models;
+
+use SilverStripe\ORM\DataObject;
+
+class ParentNode extends DataObject
+{
+    //...
+
+    private static $has_many = [
+        'ChildNodes' => BranchNode::class,
+    ];
+}
+```
+
+```php
+namespace App\Models;
+
+use SilverStripe\Forms\GridField\GridFieldConfig;
+use SilverStripe\Forms\GridField\GridFieldConfig_RecordEditor;
+use SilverStripe\ORM\DataObject;
+use Symbiote\GridFieldExtensions\GridFieldNestedForm;
+
+class ChildNode extends DataObject
+{
+    //...
+
+    private static $has_one = [
+        'ParentNode' => ParentNode::class,
+    ];
+
+    private static $has_many = [
+        'GrandChildNodes' => GrandChildNode::class,
+    ];
+
+    public function getNestedConfig(): GridFieldConfig
+    {
+        $config = new GridFieldConfig_RecordEditor();
+        $config->addComponent(GridFieldNestedForm::create()->setRelationName('GrandChildNodes'));
+
+        return $config;
+    }
+}
+```
+
+You can define your own custom GridField config for the nested GridField configuration by implementing a `getNestedConfig` on your nested model. Notice this method should return a [`GridFieldConfig`](api:SilverStripe\Forms\GridField\GridFieldConfig) object.
+
+```php
+namespace App\Models;
+
+use SilverStripe\ORM\DataObject;
+
+class GrandChildNode extends DataObject
+{
+    //...
+
+    private static $has_one = [
+        'ChildNode' => ChildNode::class,
+    ];
 }
 ```
+
+```php
+namespace App\Admin;
+
+use App\Models\ParentNode;
+use SilverStripe\Admin\ModelAdmin;
+use SilverStripe\Forms\GridField\GridFieldConfig;
+use Symbiote\GridFieldExtensions\GridFieldNestedForm;
+
+
+class MyAdminSection extends ModelAdmin
+{
+    private static string $url_segment = 'my-admin-section';
+    private static string $menu_title = 'My Admin Section';
+
+    private static array $managed_models = [
+        ParentNode::class
+    ];
+
+    protected function getGridFieldConfig(): GridFieldConfig
+    {
+        $config = parent::getGridFieldConfig();
+        $config->addComponent(GridFieldNestedForm::create()->setRelationName('ChildNodes'));
+
+        return $config;
+    }
+}
+```
+
+There is also the possibility to use Nested GridField with the data structure ArrayList. To do this, you can use the following approach.
+
+```php
+namespace App\Models;
+
+use MyDataObject;
+use SilverStripe\ORM\ArrayList;
+use SilverStripe\ORM\DataObject;
+
+class MyDataSet extends DataObject
+{
+    //...
+
+    public function getMyArrayList() {
+        $list = ArrayList::create();
+        $data = MyDataObject::get();
+
+        foreach ($data as $value) {
+            $list->push($value);
+        }
+
+        return $list;
+    }
+}
+```
+
+```php
+namespace App\Admin;
+
+use App\Models\ParentNode;
+use SilverStripe\Admin\ModelAdmin;
+use SilverStripe\Forms\GridField\GridFieldConfig;
+use Symbiote\GridFieldExtensions\GridFieldNestedForm;
+
+class MyAdminSection extends ModelAdmin
+{
+    //...
+
+    private static array $managed_models = [
+        MyDataSet::class
+    ];
+
+    protected function getGridFieldConfig(): GridFieldConfig
+    {
+        $config = parent::getGridFieldConfig();
+        $config->addComponent(GridFieldNestedForm::create()->setRelationName('getMyArrayList'));
+
+        return $config;
+    }
+}
+```
+
+Notice that instead of the name of a relation, we're passing a method name into getMyArrayList(). That method must return an instance of [`SS_List`](api:SilverStripe\ORM\SS_List) to be used in the GridField.
+
+
+#### Additional features and settings
+
+1. You can set the maximum number of nested levels using a `$default_max_nesting_level` configuration property. The default value is 10 levels.
+    ```yml
+    Symbiote\GridFieldExtensions\GridFieldNestedForm:
+        default_max_nesting_level: 5
+    ```
+
+You can also set this limitat only for a specific nested GridField using the `setMaxNestingLevel()` method.
+
+```php
+public function getNestedConfig(): GridFieldConfig
+{
+    $config = new GridFieldConfig_RecordEditor();
+    $config->addComponent(GridFieldNestedForm::create()->setMaxNestingLevel(5));
+
+    return $config;
+}
+```
+
+1. You can also modify the default config (a `GridFieldConfig_RecordEditor`) via an extension to the nested model class, by implementing
+`updateNestedConfig`, which will get the config object as the parameter.
+
+    ```php
+    namespace App\Extensions;
+
+    use SilverStripe\Core\Extension;
+
+    class NestedObjectExtension extends Extension
+    {
+        public function updateNestedConfig(GridFieldConfig &$config)
+        {
+            $config->removeComponentsByType(GridFieldPaginator::class);
+        }
+    }
+    ```