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@NogDogJun 15.2012 — #You often end up using [b]parent::[/b] to access methods/properties from the parent class. As a trivial example:
@NogDogJun 15.2012 — #Yes, it is typical to pass arguments via the parent::__construct() call. Generally, I would recommend trying to keep the parameter list the same for both parent and child constructors, so that you can use either in a given situation without having to change how you call it, but that is not required by PHP. I often have something like this in a child class:
Or in this case, perhaps your child class needs a new paramenter:
But in this case, should you ever want some sort of dynamic instantiation that decides at run-time whether to use the parent or child class, you would then also need to add logic to know whether to add that additional parameter to the instantiation. Not a huge problem, but can be a bit messy to maintain.
Constructor Arguments in Child Class Problem
At the moment I have 2 a “Photo” class and a “Photo_Small” class which extends the photo class.
Here is the code for these (simplified for readability):-
[CODE]
class Photo{
protected $src;
protected $username;
protected $size;
protected $classname = “regular”;
public function __construct($src,$username){
$this->src = $src;
$this->username = $username;
}
public function render(){
return ‘<img title=”‘.$this->username.'” class=”‘.$this->classname.'” alt=”‘.$this->username.'” width=’.$this->size.’ height=’.$this->size.’ src=”images/’.$this->src.’.jpg”>’;
}
}
class Photo_Small{
public function __construct(){
$this->size = 50;
$this->classname = “small”;
}
}
The above code works fine as long as I do this:-
[CODE]
$photo = new Photo(1,”john123″);
echo $photo->render();
However I want to be able to create small photos easily (baring in mind the Photo_Small class will have a lot more things going on in it’s constructor than in my example here) like this:-
[CODE]
$photo = new Photo_Small(1,”john123″);
echo $photo->render();
But in this last example the constructor of the Photo_Small class is overwriting the parent constructor so none of the arguments passed in are being applied.
How can I get it to work so that I can just type “new Photo_Small(1,”john123″)” and all of the arguments will be passed, the Photo constructor will fire and then the child constructor will fire?
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@NogDogJun 15.2012 — #You often end up using [b]parent::[/b] to access methods/properties from the parent class. As a trivial example:[code=php]
<?php
class Foo
{
private $test;
public function __construct()
{
$this->test = "Test";
}
public function getTest()
{
return $this->test;
}
}
class Bar extends Foo
{
private $something;
public function __construct($something)
{
$this->something = $something;
parent::__construct();
}
public function getTest()
{
return parent::getTest() . ' ' . $this->something;
}
}
$bar = new Bar('something');
echo $bar->getTest(); // "Test something"
?>[/code]0
@NogDogJun 15.2012 — #Yes, it is typical to pass arguments via the parent::__construct() call. Generally, I would recommend trying to keep the parameter list the same for both parent and child constructors, so that you can use either in a given situation without having to change how you call it, but that is not required by PHP. I often have something like this in a child class:[code=php]
public function __construct($a, $b)
{
parent::__construct($a, $b);
$this->somethingNotDoneInParentConstructor();
}
[/code]Or in this case, perhaps your child class needs a new paramenter:
[code=php]
public function __construct($a, $b, $c)
{
parent::__construct($a, $b);
$this->c = $c;
}
[/code]But in this case, should you ever want some sort of dynamic instantiation that decides at run-time whether to use the parent or child class, you would then also need to add logic to know whether to add that additional parameter to the instantiation. Not a huge problem, but can be a bit messy to maintain.