Tag: Public

Express Web Framework: Node.js

In this video tutorial we shall briefly look at Express web framework for Node.js

express-modules-file-structure-nodejs

With today’s tutorial we will be discussing the basics of Express and we’ll also be running a small example application built with Express, also we shall have a first look at Jade Template Engine.

REPL
global installation of Express Framework

C:\>npm install -g express

This installs the express globally, so that you can access it from anywhere in the system.

Also note that, you’ll need internet connection to download and install these packages.

REPL
creating express example application

C:\>cd node
C:\node>express express_example

This creates a folder and some recommended folder structure. If you’re a total beginner to Express Framework, then it’s better to stick on with these folder structure.

Now open the package.json present inside express_example folder
JSON File
package.json

{
  "name": "application-name",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node app.js"
  },
  "dependencies": {
    "express": "3.4.0",
    "jade": "*"
  }
}

It looks as shown above. It has 2 dependencies: express and jade. Install these dependencies from your command prompt / console.

REPL
installing dependencies

C:\>cd node
C:\node>cd express_example
C:\node\express_example>nmp install

This would install both express and jade, and another folder called node_modules gets created inside express_example folder.


 express-jade-modules-nodejs

Video Tutorials: Getting Started With Express Web Framework: Node.js


[youtube https://www.youtube.com/watch?v=CagrpUlQtdQ]

YouTube Link: https://www.youtube.com/watch?v=CagrpUlQtdQ [Watch the Video In Full Screen.]



Jade File
Jade to HTML

extends layout

block content
  h1= title
  p Welcome to #{title}

This jade file is present inside view folder.

jade-to-html-express-node

More about Jade Template Engine in coming videos ..

Note:


express-modules-file-structure-nodejs

Inside node_modules folder we have dependency modules.
Inside public folder javascript files, css files, images etc are present. Logical part of the application will be kept separate for security reasons.
Inside routes, routing configuration is present.
Inside views, the presentation part of the application is present. If Template Engine is used, those files will be present in this folder. Example: .jade files

app.js Starting point of execution.
package.json Contains app name, version, author, dependency module names etc.

Info: There are many popular websites built upon Express Framework, one that you might know is, MySpace!

Access Specifiers: PHP OOP

Controlling Access with public, private and protected access modifiers.
These access specifiers can be used on both variables/attributes and methods.

In this video tutorial, we’ll demonstrate it using attributes.

Access Specifiers:
1. public
2. private
3. protected

Class With Attributes

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
?>

var $a is similar to writing public $a

We shall extend class container to another class called contains.
Extending class is an inheritance property, and we shall discuss inheritance in another article. For now, know that, with extends keyword, all the properties and methods with public / protected access are inherited.

Extends

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
 
 class contains extends container
 {
 }
?>

Here, contents of class container is extended by class contains.

Object of class container

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
 
 class contains extends container
 {
 }
 
 $obj1 = new container();
         echo $obj1->a;
         echo $obj1->b;
?>

This outputs: 10 and 20 respectively.

Object of class contains

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
 
 class contains extends container
 {
 }
 
 $obj2 = new contains();
         echo $obj2->a;
         echo $obj2->b;
?>

This outputs: 10 and 20 respectively.
i.e., public attributes are inherited

Accessing private / protected attributes outside class

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
 
 class contains extends container
 {
 }
 
 $obj1 = new container();
         echo $obj1->c;
         echo $obj1->d;
?>

It through’s error, since you cannot access, private and protected variables/attributes outside the class.

Now lets check if private and protected variables are actually inherited:

Inheriting private attribute

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
 
 class contains extends container
 {
 function __construct()
{
echo $this->c;
}
 }
 
 $obj1 = new contains();
?>

This through’s error, because $c is not inherited to class contains and thus not present inside class contains. Which means, private variables and methods cannot be inherited.

Inheriting protected attribute

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< ?php
 class container
 {
 var $a       = 10;
public $b    = 20;
private $c   = 30;
protected $d = 40;
 }
 
 class contains extends container
 {
 function __construct()
{
echo $this->d;
}
 }
 
 $obj1 = new contains();
?>

Output’s 40.
This means, protected variables and methods are inherited.

Access Specifiers: PHP OOP


[youtube https://www.youtube.com/watch?v=2Ow_cgBEGmk]

YouTube Link: https://www.youtube.com/watch?v=2Ow_cgBEGmk [Watch the Video In Full Screen.]



Conclusion
public attributes and methods are inherited and can be accessed outside the class.
private attributes and methods cannot be inherited and cannot be accessed outside the class.
protected attributes and methods can be inherited but cannot be accessed outside the class.

Object Oriented Programming Basic: PHP

Video tutorial illustrates basics of OOP in PHP.

Things covered:
Defining class.
Creating Objects.
Public and Private access of Properties/Data.
Separating Class file and the application file.

What is a Class ?
A class is simply a representation of a type of object. It is the blueprint/ plan/ template that describe the details of an object. A class is the blueprint from which the individual objects are created. Class is composed of three things: a name, attributes, and operations.

Class Add
add.php

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< ?php
class Add
{
private $a;
private $b;
 
function setValues($v1, $v2)
{
   $this->a = $v1;
   $this->b = $v2;
}
 
function add()
{
return( $this->a + $this->b );
}
}
?>

class is a keyword. Add is the name of the class we’ve assigned.
$a and $b are two variables of class Add. These have private access specifier, meaning, they’re not accessible directly from outside the class.
Public access specifier indicates that they can be accessed even outside the scope of a class. Private variables are treated as safe, so we prefer that.

Since private variables are accessed inside the class, we declared two methods inside the class Add. i.e., setValues() and add()
setValues() has two parameters which are then assigned to the local variables $a and $b using the $this pointer.

$this pointer references to the object which is currently pointing to it.

add() method adds the user passed values and returns the result.

Application File
index.php

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?php
 include_once('add.php');
 
$add = new Add();
 
$add->setValues(50, 100);
echo $add->add();
 
$add->setValues(150, 100);
echo '<br />'.$add->add();
 
$add2 = new Add();
 
$add2->setValues(500, 1000);
echo '<br />'.$add2->add();
 
?>

Here we include the add.php file and create an object of (class)type Add.
Using this object we pass values to setValues(), and then call add() method, which returns the added value of the passed numbers. which is then output to the browser.

We could create as many objects as we wish and then pass and output as many results as required, without altering the class file what so ever, once finalized.

So this is the power of Object Oriented Programming.
This way we could manage complex applications easily or in an organized/standard way.
Increase code re-usability.
Also reduce maintenance cost etc..

Object Oriented Programming Basic: PHP


[youtube https://www.youtube.com/watch?v=0smq5Lf6Q2k]

YouTube Link: https://www.youtube.com/watch?v=0smq5Lf6Q2k [Watch the Video In Full Screen.]



Why OOP in PHP ?
Most web projects still use procedural i.e., function based software development approach. And honestly, it has no issue, because most web projects are so small scale and straight forward that they don’t require OOP in most cases.

But for complex application development, you need OOP for effectiveness.
Like, if you want to build a home, you need a lot of planning, preparation and some standard approach to build it.