Absolutne podstawy działania komponentów
From Joomla! Documentation
Ten artykuł jest przeznaczony dla początkujących użytkowników Joomlaǃ; ma na celu wyjaśnienie, czym jest komponent Joomlaǃ i jak działa. Gdy konkretny przykład komponentu będzie przydatny w samouczku, artykuł ten będzie odnosił się do przykładowego komponentu o nazwie Hello Worldǃ.
Czym jest komponent Joomlaǃ?
A component is a kind of Joomla! extension. Components are the main functional units of Joomla!; they can be seen as mini-applications. An easy analogy would be that Joomla! is the operating system and the components are desktop applications. Created by a component, content is usually displayed in the center of the main content area of a template (depending on the template).
Most components have two main parts: an administrator part and a site part. The site part is what is used to render pages of your site when they are requested by your site visitors during normal site operation. The administrator part provides an interface to configure and manage different aspects of the component and is accessible through the Joomla! administrator application.
Joomla! comes with a number of core components, like the content management system, contact forms and Web Links.
See also: Module, Plugin, Template
We frameworku Joomla! komponenty mogą być projektowane przy użyciu płaskiego modelu (zwraca kod HTML dla żądanej strony) lub wzorca Model-Widok-Kontroler (zwanego dalej MVC).
Wprowadzenie do MVC
MVC to wzorzec projektowy oprogramowania, który może być używany do organizowania kodu w taki sposób, że logika biznesowa i prezentacja danych są oddzielone. Założeniem tego podejścia jest to, że jeśli logika biznesowa jest zgrupowana w jednej sekcji, to interfejs i interakcja użytkownika, które otaczają dane, mogą być zmieniane i dostosowywane bez konieczności przeprogramowywania logiki biznesowej. MVC został pierwotnie opracowany w celu odwzorowania tradycyjnych ról wejścia, przetwarzania i wyjścia w logiczną architekturę GUI.
Model
Model jest częścią komponentu, która hermetyzuje dane aplikacji. Często zapewnia procedury zarządzania i manipulowania tymi danymi w znaczący sposób, oprócz procedur, które pobierają dane z modelu. Ogólnie rzecz biorąc, podstawowa technika dostępu do danych powinna być zamknięta w modelu. W ten sposób, jeśli aplikacja ma zostać przeniesiona z systemu wykorzystującego płaski plik do przechowywania informacji do systemu wykorzystującego bazę danych, model jest jedynym elementem, który należy zmienić, a nie widok lub kontroler.
Widok
The view is the part of the component that is used to render the data from the model in a manner that is suitable for interaction. For a web-based application, the view would generally be an HTML page that is returned to the user. The view pulls data from the model (which is passed to it from the controller) and feeds the data into a template which is populated and presented to the user. The view does not cause the data to be modified in any way, it only displays the data received from the model.
Controller
The controller is responsible for responding to user actions. In the case of a web application, a user action is generally a page request. The controller will determine what request is being made by the user and respond appropriately by triggering the model to manipulate the data appropriately and passing the model into the view. The controller does not display the data in the model, it only triggers methods in the model which modify the data, and then pass the model into the view which displays the data.
Joomla! Component Framework Explained
Model
In the Joomla framework, models are responsible for managing the data. The first function that has to be written for a model is a get function. It returns data to the caller. For this example, the caller will be the HelloWorldViewHelloWorld view. By default, the model named HelloWorldModelHelloWorld residing in site/models/helloworld.php is the main model associated to this view. So let's have a quick look at the naming conventions with an example, since the naming convention are the actual magic that make everything work: The class HelloWorldViewHelloWorld resides in site/views/helloworld/view.html.php and will make use of the class HelloWorldModelHelloWorld in the file site/models/helloworld.php Let's just assume we want to use an imaginary view fluffy, you would have to have: The class HelloWorldViewFluffy which resides in site/views/fluffy/view.html.php. The view will make use of HelloWorldModelFluffy in the file site/models/fluffy.php. Note: the actual screen of the view: site/views/fluffy/tmpl/default.php is required as well to make this example work. Breaking any of these bold conventions will lead to errors or a blank page.
Accessing a Joomlaǃ Component
First we need to access the Joomla! platform, which is always accessed through a single point of entry. Using your preferred web browser, navigate to the following URL:
| 1 | user access | <yoursite>/joomla/index.php |
| 2 | administrator access | <yoursite>/joomla/administrator/index.php |
Hello World! example: localhost/joomla/index.php You can use the URL of the component, or a Menu in order to navigate to the component. In this article we will discuss using the URL.
| 1 | user access | <yoursite>/joomla/index.php?option=com_<component_name> |
| 2 | administrator access | <yoursite>/joomla/administrator/index.php?option=com_<component_name> |
Hello World! example: localhost/joomla/index.php?option=com_helloworld
MVC Basic Directory Structure
Components are stored in a directory within your Joomla! installation, specifically at:
- htdocs/<path_to_joomla>/components/com_<component_name>/ .
The Hello World! component would be stored in htdocs/<path_to_joomla>/components/com_helloworld/. A basic component will contain the following files within its directoryː
- An HTML file that is just a security file with a background colorː index.html
- A PHP file that represents the controller itselfː controller.php
- A PHP file that loads the controller classː <component_name>.php
- A PHP file that represents the model itselfː models/<component_name>.php
- Another HTML file for background controlː models/index.html
- A PHP file containing the default viewː views/<component_name>/tmpl/default.php
- An XML file for adding a menu item typeː views/<component_name>/tmpl/default.xml
- Another HTML file for background controlː views/<component_name>/tmpl/index.html
- Another HTML file for background controlː views/<component_name>/index.html
- A PHP file for displaying the viewː views/<component_name>/view.html.php
JEXEC
The following line is commonly found at the start of Joomla! PHP files:
<?php
defined('_JEXEC') or die('Restricted Access');
This enables a secure entry point into the Joomla! platform. JEXEC contains a detailed explanation.
Tutorials on Designing a MVC Component
To learn how to design your own MVC Component, please complete the tutorial for your Joomla! version.