lithium\template\View

Extends lithium\core\Object

class

As one of the three pillars of the Model-View-Controller design pattern, the View class (along with other supporting classes) is responsible for taking the data passed from the request and/or controller, inserting this into the requested template/layout, and then returning the rendered content.

The View class interacts with a variety of other classes in order to achieve maximum flexibility and configurability at all points in the view rendering and presentation process. The Loader class is tasked with locating and reading template files which are then passed to the Renderer adapter subclass.

In the default configuration, the File adapter acts as both renderer and loader, loading files from paths defined in process steps (described below) and rendering them as plain PHP files, augmented with special syntax.

The View class operates on processes, which define the steps to render a completed view. For example, the default process, which renders a template wrapped in a layout, is comprised of two steps: the first step renders the main template and captures it to the rendering context, where it is embedded in the layout in the second step. See the $_steps and $_processes properties for more information.

Using steps and processes, you can create rendering scenarios to suit very complex needs.

By default, the View class is called during the course of the framework's dispatch cycle by the Media class. However, it is also possible to instantiate and call View directly, in cases where you wish to bypass all other parts of the framework and simply return rendered content.

A simple example, using the Simple renderer/loader for string templates:

$view = new View(['loader' => 'Simple', 'renderer' => 'Simple']);
echo $view->render('element', ['name' => "Robert"], ['element' => 'Hello, {:name}!']);

// Output:
"Hello, Robert!";

Note: This is easily adapted for XML templating.

Another example, this time of something that could be used in an application error handler:

$view = new View([
    'paths' => [
        'template' => '{:library}/views/errors/{:template}.{:type}.php',
        'layout'   => '{:library}/views/layouts/{:layout}.{:type}.php',
    ]
]);

$page = $View->render('all', ['content' => $info], [
    'template' => '404',
    'layout' => 'error'
]);

To learn more about processes and process steps, see the $_processes and $_steps properties, respectively.

Source

class View extends \lithium\core\Object {

	/**
	 * Output filters for view rendering.
	 *
	 * @var array List of filters.
	 */
	public $outputFilters = [];

	/**
	 * Holds the details of the current request that originated the call to this view, if
	 * applicable.  May be empty if this does not apply.  For example, if the View class is
	 * created to render an email.
	 *
	 * @see lithium\action\Request
	 * @var object `Request` object instance.
	 */
	protected $_request = null;

	/**
	 * Holds a reference to the `Response` object that will be returned at the end of the current
	 * dispatch cycle. Allows headers and other response attributes to be assigned in the templating
	 * layer.
	 *
	 * @see lithium\action\Response
	 * @var object `Response` object instance.
	 */
	protected $_response = null;

	/**
	 * The object responsible for loading template files.
	 *
	 * @var object Loader object.
	 */
	protected $_loader = null;

	/**
	 * Object responsible for rendering output.
	 *
	 * @var object Renderer object.
	 */
	protected $_renderer = null;

	/**
	 * Path used to look up view loading and rendering adapters.
	 *
	 * @var string
	 */
	protected $_adapters = 'adapter.template.view';

	/**
	 * View processes are aggregated lists of steps taken to to create a complete, rendered view.
	 * For example, the default process, `'all'`, renders a template, then renders a layout, using
	 * the rendered template content. A process can be defined using one or more steps defined in
	 * the `$_steps` property. Each process definition is a simple array of ordered values, where
	 * each value is a key in the `$_steps` array.
	 *
	 * @see lithium\template\View::$_steps
	 * @see lithium\template\View::render()
	 * @var array
	 */
	protected $_processes = [
		'all' => ['template', 'layout'],
		'template' => ['template'],
		'element' => ['element']
	];

	/**
	 * The list of available rendering steps. Each step contains instructions for how to render one
	 * piece of a multi-step view rendering. The `View` class combines multiple steps into
	 * _processes_ to create the final output.
	 *
	 * Each step is named by its key in the `$_steps` array, and can have the following options:
	 *
	 * - `'path'` _string_: Indicates the set of paths to use when loading templates.
	 *
	 * - `'conditions'` _mixed_: Make the step dependent on a value being present, or on some other
	 *    arbitrary condition. If a `'conditions'` is a string, it indicates that a key with that
	 *    name must be present in the `$options` passed to `render()`, and must be set to a
	 *    non-empty value. If a closure, it will be executed with the rendering parameters, and must
	 *    return `true` or `false`. In either case, if the condition is satisfied, the step is
	 *    processed. Otherwise, it is skipped. See the `_conditions()` method for more information.
	 *
	 * - `'capture'` _array_: If specified, allows the results of this rendering step to be assigned
	 *   to a template variable used in subsequent steps, or to the templating context for use in
	 *   subsequent steps. If can be specified in the form of `array('context' => '<var-name>')` or
	 *   `array('data' => '<var-name>')`. If the `'context'` key is used, the results are captured
	 *   to the rendering context. Likewise with the `'data'` key, results are captured to a
	 *   template variable.
	 *
	 * - `'multi'` _boolean_: If set to `true`, the rendering parameter matching the name of this
	 *   step can be an array containing multiple values, in which case this step is executed
	 *   multiple times, once for each value of the array.
	 *
	 * @see lithium\template\View::$_processes
	 * @see lithium\template\View::render()
	 * @var array
	 */
	protected $_steps = [
		'template' => ['path' => 'template', 'capture' => ['context' => 'content']],
		'layout' => [
			'path' => 'layout', 'conditions' => 'layout', 'multi' => true, 'capture' => [
				'context' => 'content'
			]
		],
		'element' => ['path' => 'element']
	];

	/**
	 * Auto-configuration parameters.
	 *
	 * @var array Objects to auto-configure.
	 */
	protected $_autoConfig = [
		'request', 'response', 'processes' => 'merge', 'steps' => 'merge'
	];

	/**
	 * Constructor.
	 *
	 * @see lithium\template\View::$_steps
	 * @see lithium\template\View::$_processes
	 * @param array $config Class configuration parameters The available options are:
	 *         - `'loader'` _mixed_: Instance or name of the class used for locating and reading
	 *           template content. Defaults to `File`, which reads template content from PHP files.
	 *         - `'renderer'` _mixed_: Instance or name of the class that populates template
	 *           content with the data passed in to the view layer, typically from a controller.
	 *           Defaults to `'File'`, which executes templates as standard PHP files, using path
	 *           information returned from the `loader` class. Both `loader` and `renderer`
	 *           classes are looked up using the `'adapter.template.view'` path, which locates
	 *           classes in the `extensions\adapter\template\view` sub-namespace of an application
	 *           or plugin.
	 *         - `'request'`: The `Request` object to be made available in the templates.
	 *           Defaults to `null`.
	 *         - `'steps'` _array_: The array of step configurations to add to the built-in
	 *           configurations. Will be merged with the defaults, with any configurations passed
	 *           in overwriting built-in steps. See the `$_steps` property for more information.
	 *         - `'processes'` _array_: The array of process steps to add to the built-in
	 *           configurations. Will be merged with the defaults, with any configurations passed
	 *           in overwriting built-in processes. See the `$_processes` property for more
	 *           information.
	 *         - `'outputFilters'` _array_: An array of filters to be used when handling output. By
	 *           default, the class is initialized with one filter, `h`, which is used in automatic
	 *           output escaping.
	 * @return void
	 */
	public function __construct(array $config = []) {
		$defaults = [
			'request' => null,
			'response' => null,
			'loader' => 'File',
			'renderer' => 'File',
			'steps' => [],
			'processes' => [],
			'outputFilters' => []
		];
		parent::__construct($config + $defaults);
	}

	/**
	 * Perform initialization of the View.
	 *
	 * Looks up and initializes loader and renderer classes, and initializes the output escape
	 * handler, matching the encoding from the `Response` object.
	 *
	 * @return void
	 */
	protected function _init() {
		parent::_init();

		$encoding = 'UTF-8';

		if ($this->_response) {
			$encoding =& $this->_response->encoding;
		}
		$h = function($data) use (&$encoding) {
			return htmlspecialchars((string) $data, ENT_QUOTES, $encoding);
		};
		$this->outputFilters += compact('h') + $this->_config['outputFilters'];

		foreach (['loader', 'renderer'] as $key) {
			if (is_object($this->_config[$key])) {
				$this->{'_' . $key} = $this->_config[$key];
				continue;
			}
			$class = $this->_config[$key];
			$config = ['view' => $this] + $this->_config;
			$this->{'_' . $key} = Libraries::instance($this->_adapters, $class, $config);
		}
	}

	/**
	 * Executes a named rendering process by running each process step in sequence and aggregating
	 * the results. The `View` class comes with 3 built-in processes: `'all'`, `'template'`, and
	 * `'element'`. The `'all'` process is the default two-step rendered view, where a template is
	 * wrapped in a layout containing a header and footer.
	 *
	 * @see lithium\template\View::_conditions()
	 * @see lithium\template\View::$_processes
	 * @see lithium\template\View::$_steps
	 * @param string $process A named set of rendering steps defined in the `$_processes` array.
	 * @param array $data An associative array of data to be rendered in the set of templates.
	 * @param array $options Options used when rendering. Available keys are as follows:
	 *              - `'type'` _string_: The type of content to render. Defaults to `'html'`.
	 *              - `'layout'` _string_: The name of the layout to use in the default two-step
	 *                 rendering process. Defaults to `null`.
	 *              - `'template'` _string_: The name of the template to render. Defaults to `null`.
	 *              - `'context'` _array_: An associative array of information to inject into the
	 *                 rendering context.
	 *              - `'paths'` _array_: A nested array of paths to use for rendering steps. The
	 *                top-level keys should match the `'path'` key in a step configuration (i.e.:
	 *                `'template'`, `'layout'`, or `'element'`), and the second level is an array
	 *                of path template strings to search (can be a string if there's only one path).
	 *                These path strings generally take the following form:
	 *                `'{:library}/views/{:controller}/{:template}.{:type}.php'`. These template
	 *                strings are specific to the `File` loader, but can take any form useful to the
	 *                template loader being used.
	 * @return string Returns the result of the rendering process, typically by rendering a template
	 *         first, then rendering a layout (using the default configuration of the `'all'`
	 *         process).
	 */
	public function render($process, array $data = [], array $options = []) {
		$defaults = [
			'type' => 'html',
			'layout' => null,
			'template' => null,
			'context' => [],
			'paths' => [],
			'data' => []
		];
		$options += $defaults;

		$data += $options['data'];
		$paths = $options['paths'];
		unset($options['data'], $options['paths']);
		$params = array_filter($options, function($val) { return $val && is_string($val); });
		$result = null;

		foreach ($this->_process($process, $params) as $name => $step) {
			if (isset($paths[$name]) && $paths[$name] === false) {
				continue;
			}
			if (!$this->_conditions($step, $params, $data, $options)) {
				continue;
			}
			if ($step['multi'] && isset($options[$name])) {
				foreach ((array) $options[$name] as $value) {
					$params[$name] = $value;
					$result = $this->_step($step, $params, $data, $options);
				}
				continue;
			}
			$result = $this->_step((array) $step, $params, $data, $options);
		}
		return $result;
	}

	/**
	 * Evaluates a step condition to determine if the step should be executed.
	 *
	 * @see lithium\template\View::$_steps
	 * @param array $step The array of instructions that define a rendering step.
	 * @param array $params The parameters associated with this rendering operation, as passed to
	 *              `render()` (filtered from the `$options` parameter).
	 * @param array $data The associative array of template variables passed to `render()`.
	 * @param array $options The `$options` parameter, as passed to `render()`.
	 * @return boolean Returns `true` if the step should be executed, or `false` if the step should
	 *         be skipped. If the step array has a `'conditions'` key which is a string, it checks
	 *         to see if the rendering options (`$options`) contain a key of the same name, and if
	 *         that key evaluates to `true`. If `'conditions'` is a closure, that closure is
	 *         executed with the rendering parameters (`$params`, `$data`, and `$options`), and the
	 *         result is determined by the return value of the closure. If a step definition has no
	 *         `'conditions'` key, it is always executed.
	 */
	protected function _conditions(array $step, array $params, array $data, array $options) {
		if (!$conditions = $step['conditions']) {
			return true;
		}
		$isCallable = is_callable($conditions) && !is_string($conditions);
		if ($isCallable && !$conditions($params, $data, $options)) {
			return false;
		}
		if (is_string($conditions) && !(isset($options[$conditions]) && $options[$conditions])) {
			return false;
		}

		return true;
	}

	/**
	 * Performs a rendering step.
	 *
	 * @see lithium\template\view\adapter\File::template()
	 * @see lithium\template\view\Renderer::render()
	 * @see lithium\template\view\adapter\File::render()
	 * @param array $step The array defining the step configuration to render.
	 * @param array $params An associative array of string values used in the template lookup
	 *              process. See the `$params` argument of `File::template()`.
	 * @param array $data associative array for template data.
	 * @param array $options An associative array of options to pass to the renderer. See the
	 *              `$options` parameter of `Renderer::render()` or `File::render()`.
	 * @return string
	 * @filter
	 */
	protected function _step(array $step, array $params, array &$data, array &$options = []) {
		$step += ['path' => null, 'capture' => null];
		$_renderer = $this->_renderer;
		$_loader = $this->_loader;
		$filters = $this->outputFilters;
		$params = compact('step', 'params', 'options') + [
			'data' => $data + $filters,
			'loader' => $_loader,
			'renderer' => $_renderer
		];

		$result = Filters::run($this, __FUNCTION__, $params, function($params) {
			$template = $params['loader']->template($params['step']['path'], $params['params']);
			return $params['renderer']->render($template, $params['data'], $params['options']);
		});

		if (is_array($step['capture'])) {
			switch (key($step['capture'])) {
				case 'context':
					$options['context'][current($step['capture'])] = $result;
				break;
				case 'data':
					$data[current($step['capture'])] = $result;
				break;
			}
		}
		return $result;
	}

	/**
	 * Converts a process name to an array containing the rendering steps to be executed for each
	 * process.
	 *
	 * @param string $process A named set of rendering steps.
	 * @param array $params
	 * @return array A 2-dimensional array that defines the rendering process. The first dimension
	 *         is a numerically-indexed array containing each rendering step. The second dimension
	 *         represents the parameters for each step.
	 */
	protected function _process($process, &$params) {
		$defaults = ['conditions' => null, 'multi' => false];

		if (!is_array($process)) {
			if (!isset($this->_processes[$process])) {
				throw new TemplateException("Undefined rendering process '{$process}'.");
			}
			$process = $this->_processes[$process];
		}
		if (is_string(key($process))) {
			return $this->_convertSteps($process, $params, $defaults);
		}
		$result = [];

		foreach ($process as $step) {
			if (is_array($step)) {
				$result[] = $step + $defaults;
				continue;
			}
			if (!isset($this->_steps[$step])) {
				throw new TemplateException("Undefined rendering step '{$step}'.");
			}
			$result[$step] = $this->_steps[$step] + $defaults;
		}
		return $result;
	}

	/**
	 * Handles API backward compatibility by converting an array-based rendering instruction passed
	 * to `render()` as a process, to a set of rendering steps, rewriting any associated rendering
	 * parameters as necessary.
	 *
	 * @param array $command A deprecated rendering instruction, i.e.
	 *              `array('template' => '/path/to/template')`.
	 * @param array $params The array of associated rendering parameters, passed by reference.
	 * @param array $defaults Default step rendering options to be merged with the passed rendering
	 *              instruction information.
	 * @return array Returns a converted set of rendering steps, to be executed in `render()`.
	 */
	protected function _convertSteps(array $command, array &$params, $defaults) {
		if (count($command) === 1) {
			$params['template'] = current($command);
			return [['path' => key($command)] + $defaults];
		}
		return $command;
	}
}

lithium\template\View

Related

Source