# ModelAdmin

## Introduction

Provides a simple way to utilize the SilverStripe CMS UI with your own data models,
and create searchable list and edit views of them, and even providing import and export of your data.

It uses the framework's knowledge about the model to provide sensible defaults,
allowing you to get started in a couple of lines of code,
while still providing a solid base for customization.

The interface is mainly powered by the `[GridField](/topics/grid-field)` class,
which can also be used in other CMS areas (e.g. to manage a relation on a `SiteTree`
record in the standard CMS interface).

## Setup

Let's assume we want to manage a simple product listing as a sample data model:
A product can have a name, price, and a category.

	:::php
	class Product extends DataObject {
	   static $db = array('Name' => 'Varchar', 'ProductCode' => 'Varchar', 'Price' => 'Currency');
	   static $has_one = array('Category' => 'Category');
	}
	class Category extends DataObject {
	   static $db = array('Title' => 'Text');
	   static $has_many = array('Products' => 'Product');
	}

To create your own `ModelAdmin`, simply extend the base class,
and edit the `$managed_models` property with the list of
data objects you want to scaffold an interface for.
The class can manage multiple models in parallel, if required.
We'll name it `MyAdmin`, but the class name can be anything you want.

	:::php
	class MyAdmin extends ModelAdmin {
	  public static $managed_models = array('Product','Category'); // Can manage multiple models
	  static $url_segment = 'products'; // Linked as /admin/products/
	  static $menu_title = 'My Product Admin';
	}

This will automatically add a new menu entry to the CMS, and you're ready to go!
Try opening http://localhost/admin/products/?flush=all.

## Search Fields

ModelAdmin uses the `[SearchContext](/reference/searchcontext)` class to provide
a search form, as well as get the searched results. Every DataObject can have its own context,
based on the fields which should be searchable. The class makes a guess at how those fields
should be searched, e.g. showing a checkbox for any boolean fields in your `$db` definition.

To remove, add or modify searchable fields, define a new `[$searchable_fields](api:DataObject::$searchable_fields)`
static on your model class (see `[SearchContext](/reference/searchcontext)` docs for details). 

	:::php
	class Product extends DataObject {
	   // ...
	   static $searchable_fields = array(
	      'Name',
	      'ProductCode'
	      // leaves out the 'Price' field, removing it from the search
	   );
	}

For a more sophisticated customization, for example configuring the form fields
for the search form, override `[api:DataObject->getCustomSearchContext()]` on your model class.

## Result Columns

The results are shown in a tabular listing, powered by the `[GridField](/topics/grid-field)`,
more specifically the `[api:GridFieldDataColumns]` component.
It looks for a `[api:DataObject::$summary_fields]` static on your model class,
where you can add or remove columns, or change their title.

	:::php
	class Product extends DataObject {
	   // ...
	   static $summary_fields = array(
	      'Name' => 'Name',
	      'Price' => 'Cost', // renames the column to "Cost"
	      // leaves out the 'ProductCode' field, removing the column
	   );
	}

## Results Customization

The results are retrieved from `[api:SearchContext->getResults()]`,
based on the parameters passed through the search form.
If no search parameters are given, the results will show every record.
Results are a `[api:DataList]` instance, so can be customized by additional
SQL filters, joins, etc (see [datamodel](/topics/datamodel) for more info).

For example, we might want to exclude all products without prices in our sample `MyAdmin` implementation.

	:::php
	class MyAdmin extends ModelAdmin {
		// ...
		function getList() {
			$list = parent::getList();
			// Always limit by model class, in case you're managing multiple
			if($this->modelClass == 'Product') {
				$list->exclude('Price', '0');
			}
			return $list;
		}
	}

You can also customize the search behaviour directly on your `ModelAdmin` instance.
For example, we might want to have a checkbox which limits search results to expensive products (over $100).

	:::php
	class MyAdmin extends ModelAdmin {
		// ...
		function getSearchContext() {
			$context = parent::getSearchContext();
			if($this->modelClass == 'Product') {
				$context->getFields()->push(new CheckboxField('q[ExpensiveOnly]', 'Only expensive stuff'));
			}
			return $context;
		}
		function getList() {
			$list = parent::getList();
			$params = $this->request->requestVar('q'); // use this to access search parameters
			if($this->modelClass == 'Product' && isset($params['ExpensiveOnly']) && $params['ExpensiveOnly']) {
				$list->exclude('Price:LessThan', '100');
			}
			return $list;
		}
	}

## Managing Relationships

Has-one relationships are simply implemented as a `[api:DropdownField]` by default.
Consider replacing it with a more powerful interface in case you have many records
(through customizing `[api:DataObject->getCMSFields]`).

Has-many and many-many relationships are usually handled via the `[GridField](/topics/grid-field)` class,
more specifically the `[api:GridFieldAddExistingAutocompleter]` and `[api:GridFieldRelationDelete]` components.
They provide a list/detail interface within a single record edited in your ModelAdmin.

## Permissions

`ModelAdmin` respects the permissions set on the model, through methods on your `DataObject` implementations:
`canView()`, `canEdit()`, `canDelete()`, and `canCreate`.

In terms of access control to the interface itself, every `ModelAdmin` subclass
creates its own "[permission code](/reference/permissions)", which can be assigned
to groups through the `admin/security` management interface. To further limit
permission, either override checks in `ModelAdmin->init()`, or define
more permission codes through the `ModelAdmin::$required_permission_codes` static.

## Data Import

The `ModelAdmin` class provides import of CSV files through the `[api:CsvBulkLoader]` API.
which has support for column mapping, updating existing records,
and identifying relationships - so its a powerful tool to get your data into a SilverStripe database.

By default, each model management interface allows uploading a CSV file
with all columns autodetected. To override with a more specific importer implementation,
use the `[api:ModelAdmin::$model_importers] static.

## Data Export

Export is also available, although at the moment only to the CSV format,
through a button at the end of a results list. You can also export search results.
It is handled through the `[api:GridFieldExportButton]` component.

To customize the exported columns, create a new method called `getExportFields` in your `ModelAdmin`:

	:::php
	class MyAdmin extends ModelAdmin {
		// ...
		function getExportFields() {
			return array(
				'Name' => 'Name',
				'ProductCode' => 'Product Code',
				'Category.Title' => 'Category'
			);
		}
	}

Dot syntax support allows you to select a field on a related `has_one` object.

## Extending existing ModelAdmins

Sometimes you'll work with ModelAdmins from other modules, e.g. the product management
of an ecommerce module. To customize this, you can always subclass. But there's
also another tool at your disposal: The `[api:Extension]` API.

	:::php
	class MyAdminExtension extends Extension {
		// ...
		function updateEditForm(&$form) {
			$form->Fields()->push(/* ... */)
		}
	}

	// mysite/_config.php
	Object::add_extension('MyAdmin', 'MyAdminExtension');

The following extension points are available: `updateEditForm()`, `updateSearchContext()`,
`updateSearchForm()`, `updateList()`, `updateImportForm`.

## Customizing the interface

Interfaces like `ModelAdmin` can be customized in many ways:

 * JavaScript behaviour (e.g. overwritten jQuery.entwine rules)
 * CSS styles
 * HTML markup through templates

In general, use your `ModelAdmin->init()` method to add additional requirements
through the `[Requirements](/reference/requirements)` API.
For an introduction how to customize the CMS templates, see our [CMS Architecture Guide](/reference/cms-architecture).

## Related

*  `[api:SearchContext]`
* [genericviews Module](http://silverstripe.org/generic-views-module)
* [Presentation about ModelAdmin at SupperHappyDevHouse Wellington](http://www.slideshare.net/chillu/modeladmin-in-silverstripe-23)
* [Reference: CMS Architecture](../reference/cms-architecture)
* [Howto: Extend the CMS Interface](../howto/extend-cms-interface)