virtualbox ubuntu boot menu delay and reset password

To increase boot menu delay, first get a list of vms by typing the following in a terminal.

 VBoxManage list vms

You can change the delay by typing:

VBoxManage modifyvm "You virtual machine name from above command" --bioslogodisplaytime 10000

Now start/restart the Ubuntu machine and hold down the left SHIFT key from keyboard unless you get the boot menu. Select ‘root …’ from menu.
We need need to remount the disk in read-write mode:

mount -rw -o remount /

Change the password of the required user, lets say user1:

passwd user1
...

The state object

The state object contains the main data object of the application. Anything that changes in the state object will re-render the component.

The related method to set a specific key in the state is setState. The set state could be called after componentDidMount is called.

 

    constructor(props) {
      super(props);
      this.state = { products: [...] };
    }

    componentDidMount() {
      ....
      this.setState({products});
      .....
    }

Chain pattern


require "vendor/autoload.php";

use Chain\HomeStatus;
use Chain\Lock;
use Chain\Lights;
use Chain\Alarm;


$lock = new Lock();
$lights = new Lights();
$alarm = new Alarm();

$lock->setSuccessor($lights);
$lights->setSuccessor($alarm);

$homeStatus = new HomeStatus();
$lock->check($homeStatus);
echo PHP_EOL;


Strategy pattern


namespace Stra;

use Stra\Logger;
use Stra\DatabaseLogger;
use Stra\FileLogger;

class Strategy
{
    public function log($msg, Logger $logger = null)
    {
        if(is_null($logger)) {
            $logger = new DatabaseLogger();
        }

        $logger->log($msg);
    }
}

Test Drive


require 'vendor/autoload.php';

use Stra\Strategy;
use Stra\FileLogger;
use Stra\DatabaseLogger;

$app = new Strategy();
$app->log('Some action happened.', new FileLogger());

Factory pattern

Code


namespace Patterns;


/**
 * Design pattern - Factory
 *
 * @author: Hazrat Ali
 * @mail: iloveyii@yahoo.com
 * Date: 2016-07-30
 */
class ShapeFactory
{
    private static $types = ['Rectangle', 'Square'];

    public static function create($type)
    {
        if( ! in_array($type, self::$types)) {
            die('Invalid type ' . $type . ', valid types are ' . implode(',', self::$types) . EOL);
        }

        if($type == 'Rectangle') {
            return new Rectangle(50, 15);
        }

        if($type == 'Square') {
            return new Square(20);
        }
    }
}


SingletonX

Git repo


namespace Patterns;


/**
 * Design pattern - Singleton extended
 * The extended version contains an array of instances
 *
 * @author: Hazrat Ali
 * @mail: iloveyii@yahoo.com
 * Date: 2016-07-30
 */
class SingletonX
{
    private static $instances = [];
    private $dir = 'tr';
    private $language;
    private $translations;

    public function __construct($language)
    {
        $this->language = $language;
        $this->readTranslationFile('string.json');

        echo 'Object initiated with language ' , $language . EOL;
    }

    public static function getInstance($language)
    {
        if( ! isset(self::$instances[$language])) {
            self::$instances[$language] = new self($language);
        }

        return self::$instances[$language];
    }

    public function translate($text)
    {
        return isset($this->translations[$text]) ? $this->translations[$text] : false;
    }

    private function readTranslationFile($fileName)
    {
        $filePath = $this->getPathAbs($fileName);

        if(file_exists($filePath)) {
            $contents = file_get_contents($filePath);
        } else {
            $svContents = json_encode([
                'language'=>'språk',
                'code'=>$this->language,
                'country'=>'land',
                'city'=>'stad'
            ]);
            $frContents = json_encode([
                'language'=>'la langue',
                'code'=>$this->language,
                'country'=>'pays',
                'city'=>'ville'
            ]);

            if($this->language == 'sv') {
                file_put_contents($filePath, $svContents);
                $contents = $svContents;
            }

            if($this->language == 'fr') {
                file_put_contents($filePath, $frContents);
                $contents = $frContents;
            }
        }

        $this->translations = json_decode($contents, JSON_FORCE_OBJECT);
    }

    private function getPathAbs($fileName)
    {
        $path = sprintf("%s/%s/%s/%s", dirname(__FILE__), $this->dir, $this->language, $fileName);

        if( ! file_exists(dirname($path))) {
            mkdir(dirname($path), 0777, true);
        }

        return $path;
    }
}

Singleton pattern

Code

The singleton pattern is used to restrict the creation of only object of a class. This is useful when it is expensive (in terms of resources) to initiate new objects every time the same object is needed. This pattern specifically put this logic of maintaining only one instance inside the class itself.

This pattern can be used in situations like database connectivity, reading and writing to disk, sending emails.

In the example below we use a simple translation class which read a json file with translations. Only one instance is needed since reading file operations are slower. Therefore we can easily use this object as many times as needed for multiple words translation. Since it is a singleton so it will keep only one instance each time we use it in the code.

namespace Patterns;


/**
 * Design pattern - Singleton
 * @author: Hazrat Ali
 * @mail: iloveyii@yahoo.com
 * Date: 2016-07-30
 */
class Singleton
{
    private static $instance;
    private $dir = 'tr';
    private $language;
    private $translations;

    public function __construct($language)
    {
        $this->language = $language;
        $this->readTanslationFile('string.json');
    }

    public static function getInstance($language)
    {
        if( ! isset(self::$instance)) {
            self::$instance = new self($language);
        }

        return self::$instance;
    }

    public function translate($text)
    {
        return isset($this->translations[$text]) ? $this->translations[$text] : false;
    }

    private function readTanslationFile($fileName)
    {
        $filePath = $this->getPathAbs($fileName);

        if(file_exists($filePath)) {
            $contents = file_get_contents($filePath);
        } else {
            $contents = json_encode([
                'language'=>'språk',
                'code'=>$this->language,
                'country'=>'land',
                'city'=>'stad'
            ]);

            file_put_contents($filePath, $contents);
        }

        $this->translations = json_decode($contents, JSON_FORCE_OBJECT);
    }

    private function getPathAbs($fileName)
    {
        $path = sprintf("%s/%s/%s/%s", dirname(__FILE__), $this->dir, $this->language, $fileName);

        if( ! file_exists(dirname($path))) {
            mkdir(dirname($path), 0777, true);
        }

        return $path;
    }
}