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2015-05-22T21:12:24Z
Created page with "<pre class="prettyprint"> <?php  /**  * Event Bus Challenge  *   * FIRST: COPY/PASTE ALL THIS CODE IN THE TEXTFIELD BELOW AND EDIT IT THERE  *   * 1. The goal is to build a ve..."
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<?php



/**

 * Event Bus Challenge

 * 

 * FIRST: COPY/PASTE ALL THIS CODE IN THE TEXTFIELD BELOW AND EDIT IT THERE

 * 

 * 1. The goal is to build a very simple PubSub/event class in PHP. 

 *    We will create an EventEmitter object and then we'll subscribe to events and trigger them. 

 *    Subscribing to an event simply adds a callback to be run when the event is triggered. 

 *    Triggering an event (emit) should run all the attached callbacks.

 * 2. Don't overthink it. The solution should only take a few minutes and a few lines of code. 

 *    Build only what you need to get the desired ouput.

 * 

 * Constraints:

 * 1. Although we only use error/success events, please build the class to handle arbitrary events.

 * 2. Events data will always be an associative array.

 * 3. A callback should always be safe to call.

 */



class EventEmitter {



    var $current_callback;

    

    public function __construct() {

        // no special needs I can see

        $this->current_callback = array();

    }



    public function emit($description , $data) {

        // emit an message using previsouly subscribed function

        // loop through all the previous functions.

        if (!empty($this->current_callback[$description])) {

            foreach ($this->current_callback[$description] as $current) {

                call_user_func($current, $data);

            }

        }

    }



    public function subscribe($description, $callback_func_name) {

        // callback function specified. 

        // add to array

        if (empty($this->current_callback[$description])) {

            $this->current_callback[$description] = array();

        }

        $this->current_callback[$description][] = $callback_func_name;

    }



}



$emitter = new EventEmitter;



$error_callback = function($data) {

    echo "Error 1. {$data["message"]} \n";

};



$error_callback2 = function($data) {

    echo "Error 2. {$data["message"]} \n";

};



$success_callback = function($data) {

    echo "SUCCESS! {$data["message"]} \n";

};



$emitter->emit("error", ["message" => "Error one."]);



$emitter->subscribe("error", $error_callback);

$emitter->emit("error", ["message" => "Second error."]);



$emitter->subscribe("error", $error_callback2);

$emitter->emit("error", ["message" => "Yet another error."]);



$emitter->subscribe("success", $success_callback);

$emitter->emit("success", ["message" => "Great success!."]);



// Expected output:



// Error 1. Second error.

// Error 1. Yet another error.

// Error 2. Yet another error.

// SUCCESS! Great success!

</pre>
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