instanciation best practice sub class

[elquijote]

Hello World,

I have what may seem like a dumb question. Maybe what I am trying to do should be done differently. This question is both a "best practice" and "help with code." I am very new to OOP so please excuse the ignorance. Within the code examples below you will find other questions.

 

Lets pretend I have a page that I want to create a new "Roll" class. The Roll class has a function to scan folder for all files of type jpeg. I need instances for each thing returned in this scan be associated with a new type Picture.

 

Should picture extend class roll????

 

class Roll{

private $roll_id;

private $roll_date;

private $roll_pict_array = array();

 

 

// special __functions //

public function __constructor(){

//////////////////////////QUESTION 1

// It seems like I should use the constructor for something but I cant find a reason for it.

//I know that anything with in the constructor gets executed when an instance is created but i cant seem to fathom a practical use. books haven't helped in this department

 

}

public function scanPictureFolder(){

$dir_to_read = "/Users/quijote/Sites/_tempdata/";

 

while (false !== ($file = readdir($handle))) {

if($file !="." && $file !=".." && preg_match("/\.jpg$|\.jpeg$/i", $file)){

array_push($this->roll_pict_array, $dir_to_read.$file);

 

//////////////////////////QUESTION 2

// Instead of doing the array_push and then using the createPictureInstance below I should just create an instance here of picture here for each thing returned. I cant seem to figure which is the best practice.

}

}

    }

 

    public function createPictureInstance(){

//$numpicts = count($this->roll_pict_array);

//if($i=0;$i<$numpicts;$i++){

foreach($this->roll_pict_array as $element){

//echo($element);

 

}

}

}

I would like to create a new instance of Picture for each file found. I would like these Pictures to be associated with Roll.

 

[genericnumber1]

If what you meant is you would like to do is fill an array in Roll with a new picture instance you could do something like this...

 

<?php
/**
* This probably doesn't match your intent (since Roll made no sense to me I changed the class name)
* This is just an example to help explain what I think you're saying is your problem
* I also used constructors to show you a use for them
*/
class Dir
{
private $directory;
private $contents;

// Set the directory
// We use a construct since a "Directory" class should never be without a directory set
public function __construct($directory)
{
	$this->directory = $directory;
	$this->updateContents();
}

// Update the contents of current directory
public function updateContents()
{
	$contents = scandir($this->directory);
	foreach($contents as $item)
	{
		if($item != '.' && $item != '..')
		{
			$this->contents[] = $item;
		}
	}
}

// Search the directory for all JPEG images
public function getPictures()
{
	$pictures = array(); // Set an array to put the pictures in
	foreach($this->contents as $fileName)
	{
		if(preg_match("/\.jpg$|\.jpeg$/i", $fileName))
		{
			$pictures[] = new Picture($this->directory, $fileName);
		}
	}
	return $pictures;

}
}

class Picture
{
private $directory;
private $fileName;

// Set the directory and the file name
// We use a construct since a "Picture" should never be without a location
public function __construct($directory, $fileName)
{
	$this->directory = $directory;
	$this->fileName = $fileName;
}

// Maybe a function to make use of the class
public function getLocation()
{
	return $this->directory . '/' . $this->fileName;
}
}

// Test the class out...
$directory = new Dir('C:\Documents and Settings\Matthew\Desktop\Files\Misc\Other Images');
$pictures = $directory->getPictures();

// Get the first image location... (if it exists)
if(isset($pictures[0]))
{
echo $pictures[0]->getLocation();
}
else {
echo 'There is no $picture[0]';
}
?>

 

You normally shouldn't "extend" a class unless you mean to make a more specialized version of a class...

For example...

Animal -> Feline -> House Cat

 

or a more in-the-wild example...

Controller -> ApplicationController -> NewsController