Controllers & AJAX

#Introduction

The Winter CMS backend implements the MVC pattern. Controllers manage backend pages and implement various features like forms and lists. This article describes how to develop backend controllers and how to configure controller behaviors.

Each controller consists of a PHP file which resides in the the /controllers subdirectory of a Plugin directory. Controller views are .php files that reside in the controller view directory. The controller view directory name matches the controller class name written in lowercase. The view directory can also contain controller configuration files. An example of a controller directory structure:

plugins/
`-- acme/
    `-- blog/
        |-- controllers/
        |   |-- users/                 # Controller view directory
        |   |   |-- _partial.php       # Controller partial file
        |   |   |-- config_form.yaml   # Controller config file
        |   |   `-- index.php          # Controller view file
        |   `-- Users.php              # Controller class
        `-- Plugin.php

#Class definition

Controller classes must extend the \Backend\Classes\Controller class. As any other plugin class, controllers should belong to the plugin namespace. The most basic representation of a Controller used inside a Plugin looks like this:

namespace Acme\Blog\Controllers;

class Posts extends \Backend\Classes\Controller {

    public function index()    // <=== Action method
    {

    }
}

Usually each controller implements functionality for working with a single type of data - like blog posts or categories. All backend behaviors described below assume this convention.

#Controller properties

The backend controller base class defines a number of properties that allow to configure the page appearance and manage the page security:

#Actions, views and routing

Public controller methods, called actions are coupled to view files which represent the page corresponding the action. Backend view files use PHP syntax. Example of the index.php view file contents, corresponding to the index action method:

<h1>Hello World</h1>

URL of this page is made up of the author name, plugin name, controller name and action name.

backend/[author name]/[plugin name]/[controller name]/[action name]

The above Controller results in the following:

https://example.com/backend/acme/blog/users/index

#Passing data to views

Use the controller's $vars property to pass any data directly to your view:

$this->vars['myVariable'] = 'value';

The variables passed with the $vars property can now be accessed directly in your view:

<p>The variable value is <?= $myVariable ?></p>

#Setting the navigation context

Plugins can register the backend navigation menus and submenus in the plugin registration file. The navigation context determines what backend menu and submenu are active for the current backend page. You can set the navigation context with the BackendMenu class:

BackendMenu::setContext('Acme.Blog', 'blog', 'categories');

The first parameter specifies the author and plugin names. The second parameter sets the menu code. The optional third parameter specifies the submenu code. Usually you call the BackendMenu::setContext in the controller constructor.

namespace Acme\Blog\Controllers;

class Categories extends \Backend\Classes\Controller {

public function __construct()
{
    parent::__construct();

    BackendMenu::setContext('Acme.Blog', 'blog', 'categories');
}

You can set the title of the backend page with the $pageTitle property of the controller class (note that the form and list behaviors can do it for you):

$this->pageTitle = 'Blog categories';

#Using AJAX handlers

The backend AJAX framework uses the same AJAX library as the frontend pages. The library is loaded automatically on the backend pages.

#Backend AJAX handlers

The backend AJAX handlers can be defined in the controller class or widgets. In the controller class the AJAX handlers are defined as public methods with the name starting with "on" string: onCreateTemplate, onGetTemplateList, etc.

Backend AJAX handlers can return an array of data, throw an exception or redirect to another page (see AJAX event handlers). You can use $this->vars to set variables and the controller's makePartial method to render a partial and return its contents as a part of the response data.

public function onOpenTemplate()
{
    if (Request::input('someVar') != 'someValue') {
        throw new ApplicationException('Invalid value');
    }

    $this->vars['foo'] = 'bar';

    return [
        'partialContents' => $this->makePartial('some-partial')
    ];
}

#Triggering AJAX requests

The AJAX request can be triggered with the data attributes API or the JavaScript API. Please see the frontend AJAX library for details. The following example shows how to trigger a request with a backend button.

<button
    type="button"
    data-request="onDoSomething"
    class="btn btn-default">
    Do something
</button>

NOTE: You can specifically target the AJAX handler of a widget using a prefix widget::onName. See the widget AJAX handler article for more details.

#Controller middleware

You can define middleware in your backend controllers, providing you with a convenient mechanism for making changes to the response of a HTTP request. For example, you may wish to specify a HTTP header for certain actions in your controller, or redirect users if they don't meet certain criteria.

Controller middleware is executed after the request is processed by Winter CMS, but before the response is sent to the browser.

To define middleware for your controller, you may specify it in the __construct() method of your backend controller by calling the middleware() method.

public function __construct()
{
    parent::__construct();

    $this->middleware(function ($request, $response) {
        // Middleware functionality
    });
}

The middleware() method requires a callback with two arguments, $request providing the request information and $response providing the response object. The callback should return the $response object with your modifications.

As an example, to add a Test-Header header to your response, you could do the following:

public function __construct()
{
    parent::__construct();

    $this->middleware(function ($request, $response) {
        $response->headers->set('Test-Header', 'Test');
        return $response;
    });
}

You can also control which actions will use your middleware by using the only() and except() modifiers. For example, to restrict the middleware to only run on the index action, you could do the following:

public function __construct()
{
    parent::__construct();

    $this->middleware(function ($request, $response) {
        // Middleware functionality
    })->only('index');
}

Alternatively, to run the middleware on every action except the index action:

public function __construct()
{
    parent::__construct();

    $this->middleware(function ($request, $response) {
        // Middleware functionality
    })->except('index');
}