wordpress-like model to view api event system (MVC) - php

Question

Wordpress has a nice api system. I'm struggling in creating an equal flexible one using a more traditional MVC interpretation. A typical view class could be like this:
class View
{
public function set($name, $value)
{
$this->data[$name] = $value
}
public function __get($name) ... you know how it works
}
A use case would be a controller adding an order contain order lines:
$view->add('order', $orderModel);
Then the template file could have something like
foreach ($this->order->getOrderLines() as $orderLine)
{
?><div><?php echo $orderLine->getItemName(); ?><div><?php
}
At least this is what is commonly seen in many PHP MVC frameworks. I'm open to alternative implementations that solve the question:
How to add an event system like wordpress has? Eg a filter OrderLineItemName.

Answer 1

Okay,
I am not 100% exactly what you want to do, but I have an idea.
Maybe you mean something like this:
class View {
public $hooks = array('getsomeVar');
public $hooks_functions = array();
public $attributes = array();
public function __set($k,$v) {
$this->attributes[$k] = $v;
}
public function __get($k) {
if (isset($this->attributes[$k])){
$hooks = $this->get_functions_by_hook('get' . $k);
if (!empty($hooks)){
foreach ($hooks as $klass=>$methods) {
if (class_exists($klass)){
$class = new $klass();
foreach ($methods as $method) {
if (method_exists($class,$method)){
$this->attributes[$k] = $class->$method($this->attributes[$k]);
}
}
}
}
}
return $this->attributes[$k];
} else {
throw new Exception($k . " is not a view variable");
}
}
public function register_filter($name,$class,$method) {
if (in_array($name,$this->hooks)){
$this->hooks_functions[$name][$class][] = $method;
} else {
throw new Exception($name . ' is not a valid hook');
}
}
public function get_functions_by_hook($name) {
if (array_key_exists($name,$this->hooks_functions)){
return $this->hooks_functions[$name];
}
return array();
}
}
class MyPlugin {
public function fix_string($str) {
return str_replace("ruby",'php',$str);
}
}
$v = new View();
$v->someVar = 'ruby is great';
$v->register_filter('getsomeVar','MyPlugin','fix_string');
echo $v->someVar;
or you can use this method, which is more event like. Again sample code, but you should be able to cannabalize it.
class EventDispatcher {
public static $listeners = array();
public static function registerListener(&$instance) {
if (!in_array($isntance,self::$listeners)){
array_push(self::$listeners,$instance);
}
}
public static function dispatchEvent($name,&$value) {
foreach (self::$listeners as $listener) {
if (method_exists($listener,'interests')){
$funcs = $listener->interests();
if (array_key_exists($name,$funcs)){
foreach ($funcs as $f) {
$value = $listener->$f($value);
}
}
}
}
}
}
class Plugin {
public static function registerPlugin($class_name) {
if (class_exists($class_name)){
EventDispatcher::registerListener(new $class_name());
}
}
}
class Model {
public function __construct() {
EventDispatcher::registerListener($this);
}
public function special($value) {
echo "I got called too!\n\n";
return $value;
}
public function interests() {
return array(
"getsomeVar" => "special",
);
}
}
class View {
public $attributes = array();
public function __set($k,$v) {
$this->attributes[$k] = $v;
}
public function __get($k) {
if (isset($this->attributes[$k])){
EventDispatcher::dispatchEvent('get' . $k,$this->attributes[$k]);
return $this->attributes[$k];
} else {
throw new Exception($k . " is not a view variable");
}
}
}
class MyPlugin {
public function fix_string($str) {
return str_replace("ruby",'php',$str);
}
public function interests() {
return array(
"getsomeVar" => "fix_string",
);
}
}
Plugin::registerPlugin('MyPlugin');
$model = new Model();
$v = new View();
$v->someVar = 'ruby is great';
echo $v->someVar;
This is just some sample code, I don't do it this way at all, but it seems like it may be what you are talking about.
Cheers,
Jason
Addendum:
Most of this stuff is about the WP codebase.
WP accesses variables set in the global scope that are modified like so:
function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
global $wp_filter, $merged_filters;
$idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
$wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
unset( $merged_filters[ $tag ] );
return true;
}
It has some other functions like, has_filter etc...
function apply_filters($tag, $value) {
global $wp_filter, $merged_filters, $wp_current_filter;
$args = array();
$wp_current_filter[] = $tag;
// Do 'all' actions first
if ( isset($wp_filter['all']) ) {
$args = func_get_args();
_wp_call_all_hook($args);
}
if ( !isset($wp_filter[$tag]) ) {
array_pop($wp_current_filter);
return $value;
}
// Sort
if ( !isset( $merged_filters[ $tag ] ) ) {
ksort($wp_filter[$tag]);
$merged_filters[ $tag ] = true;
}
reset( $wp_filter[ $tag ] );
if ( empty($args) )
$args = func_get_args();
do {
foreach( (array) current($wp_filter[$tag]) as $the_ )
if ( !is_null($the_['function']) ){
$args[1] = $value;
$value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
}
} while ( next($wp_filter[$tag]) !== false );
array_pop( $wp_current_filter );
return $value;
}
This is not an event driven system, it's a method lookup table which is just a giant hash that looks up the user defined functions to call.
apply_filters, and all plugin like functions are called procedurally as the code is rendered, here is an example
if ( $prefixed ) {
$value = apply_filters("pre_$field", $value);
$value = apply_filters("${field_no_prefix}_save_pre", $value);
} else {
$value = apply_filters("pre_post_$field", $value);
$value = apply_filters("${field}_pre", $value);
}
Or for actions, in an actual template view like so:
<p class="submit"><input type="submit" class="button" name="submit" value="<?php esc_attr_e('Add Category'); ?>" /></p>
<?php do_action('edit_link_category_form', $category); ?>
</form>