Languages – Page 3 – Coding Friends

Final and auto load a class

To include a class within many languages you have to define it at the top and then off you go with programming with using that class. Well within PHP you can use the __autoload function that is called when you try to create a new instance of a class.

function __autoload($class_name) 
{
	include "classes/".$class_name.".php";
}

this __autoload function above takes a parameter as the class name to load and then within the code it will try and load that class with how ever you want to, in this case I have placed the classes within the directory called classes and under there classname.php filename.

So if you try to load the class

$newclass = new basic();

it will look within the classes directory for the file basic.php for the autoload function above, you can alter it to load from where ever and how ever you want to.

The next part of this post is about the keyword ‘final’, the final keyword means that it is final so if you try and extend that class and extend the function that has been declared as final this will cause php interpretor to fail due to syntax error with something similar to

Fatal error: Cannot override final method class_name::function_name()

For an example here is two classes one is called basic and the other is called extendbasic, where the basic class has the final function within it

class basic
{
	public function sayHello()
	{
		echo "<br/>".get_class($this) . " : Hello";
	}
 
	final public function sayGoodbye()
	{
		echo "<br/>".get_class($this) . " : Goodbye";
	}
}

and here is the extendclass

class extendbasic extends basic
{
	public function sayHello()
	{
		echo "<br/>".get_class($this). " : the newer hello!!";	
		parent::sayHello();
	}
        // this will cause the php engine to fail!!!!!. because it is trying to over load the function sayGoogbye which has been declared as final
/*	public function sayGoodbye()
	{
		echo "I should not get here!!";
	}*/
}

Here is some code to call them both which they have been placed within a directory called ‘classes’

function __autoload($class_name) 
{
	include "classes/".$class_name.".php";
}
 
$basicClass = new basic();
$basicClass->sayHello();
$basicClass->sayGoodbye();
$basicClass = new extendbasic();
$basicClass->sayHello();
$basicClass->sayGoodbye();

and the output would be

basic : Hello
basic : Goodbye
extendbasic : the newer hello!!
extendbasic : Hello
extendbasic : Goodbye

I am calling the parent function from within the extendbasic class sayHello function.

Ckeditor – not allow posting of images from the local harddrive

Within the CKEditor you can also add on to the prototypes that allow more control of what is allowed on your website.

Sometimes you do not want to allow the user to copy and paste local files to the CKEditor so this is what I done to remove the file:// from within the img tag within the copy and paste with using the CKEditor htmlDataProcessor group of functions, in this case the ‘toHtml’ function which is called when the user pastes any content into the CKEditor window. All I am doing it using the regular expression to search for the <img src=”file .. and replace with a <mg tag> which when they double click on that it will open the CKEditor’s image browser (which you can include a upload part to it as well 🙂 )

CKEDITOR.htmlDataProcessor.prototype.toHtml = function( data, fixForBody )
  {
    return data.replace(/\<img src=\"file:([^\>])*\>/ig,"<img title=\"Please use the Media/Image uploader because can not show files on your harddrive\" alt=\"Please use the Media/Image uploader because can not show files on your harddrive\"/>");
}

It was very helpful for me.

Classes

Since Python is a object oriented programming language then you can use things like classes to define a object, a class is a bunch of methods that act on the data that is stored within the class itself. You can store data within the class, but unlike c++/java/c# etc, there is no private/public/protected, everything is public accessible.

In the example below, the class constructor is called (__init__ method) and the first parameter is the class object itself, which is why it is there and for many reasons why it is called self as a variable name.

 
#  self means the object itself.
 
class mysimpleclass :
        __myvar = 0
        def __init__(self,value = 0) :
                self.__myvar = value
 
        def printValue(self) :
                print self.__myvar
 
simple = mysimpleclass(5)
simple.printValue()

the printValue method just does that, it will print the value that is sorted within the class object and here is the output

if you did not put in the self in the example above for printing out the class object variable __myvar as below

class mysimpleclass ....
       ....
       def printValue() :
            print __myvar

the error would be

NameError: global name '_mysimpleclass__myvar' is not defined

because the interrupter is looking for a global variable and not a variable attached to that object.

Add two numbers

To carry on my normal process of notes on this website for different languages here is the how to add two numbers with a return value from a function.

To define a function you use the “def” syntax within the programming language and then the next bit of text before the parameters for the function itself ( in this case the parameters are the (number1, number2) ), is the function name and how to call the function.

The function below takes two parameters and returns back there result of the mathematical addition, the last part is how to call the function.

def addTwo(number1, number2) : 
	return number1 + number2
 
print addTwo(1,2)

and the output would be

Read / Write

Here is how to open and read/write to a file within Python. Most languages supply a basic file opening and read/writing methods with the closing method, and Python is no different which makes going from one language to another very easy (you just need to learn the classes that are capable to doing the interesting stuff 🙂 ).

To write to a file, you have to open it first within a write mode (‘w’) and then write to that file *handler*, in the code below the variable ‘f’ is the file *handler*

f = open('write.txt','w');
f.write('hi there\n');
f.write('this is genux\n');
f.write('and my site is codingfriends.com\n');
f.write('pyhon does OO\n');
f.close();
print 'File has been written\n';

which will write to the “write.txt” the following text

hi there
this is genux
and my site is codingfriends.com
pyhon does OO

and then to read in the file you use the read mode ‘r’, you are able to use the Iterator style of coding with using a ‘for in :’ or if you wish to read one line at a time you can use the ‘readline()’ method, and to seek within a file you use the method ‘seek()’.

f = open('write.txt','r');
for readInLine in f:
	print readInLine;
 
print 'seek to the start of the file';
f.seek(0);
anotherLine = f.readline();
print anotherLine;
 
f.close();

and here is the output

hi there
 
this is genux
 
and my site is codingfriends.com
 
pyhon does OO
 
seek to the start of the file
hi there

Hello world

Python is one of those languages that are used by allot of different companies but probably does not get the credit that how much it is used. Google uses it, allot of the Ubuntu backend is python. Python is able to do object orientated programming, but does not include the full essence of objects like other languages like C++/Java/C# where you have a private/public/protected but use a “__” before the variable as a “hidden” variable within the class.

So going to do some posts of how cool Python can be, but to start with the classic “hello world” program, like most languages (C++/PHP/C#/Java) most of the functions/methods are actually english words that should mean something to the writer/reader of the program, so to display a message to the screen you can use the “print” command and here is the example program

print "hello world"

and this will output, if you save out that program as helloworld.py

hello world

to call the saved program via the command line you need to call the interpreter (the python program).

python helloworld.py

Javascript {} []

Someone asked me what is the difference between {} and [] within javascript.

Basically the difference is one is a key => value pair like PHP ‘{}’, and the other is just a pure array of values ‘[]’.

Here is the code.

var simplearray = ["genux","linux"];
 
var keyvaluearray = {"name" : "genux", "OS" : "linux"};

To access the different values, since the simple array is index by numbers 0 onwards you use the [x] notation, and the key value array you can reference the value by the name of the key like in object orientated way.

alert(simplearray[0]);
 
alert(keyvaluearray.name);