I have two classes. A child and a parent. The parent is calling a static method from the child (that's an overriden static parent method in the child class) and I get a general server error.
When I remove the relation ('extends' part), all is fine and get no errors. No idea why. Can't you override static methods? Looked for answers but can't seem to find them.
Class Fase {
public static function getbyId($id) {
//some stuff
}
public function getsomefaseitem($fase_item_id) {
FaseItem::getbyid($fase_item_id);
}
}
Class FaseItem extends Fase {
public static function getbyId($id) {
}
}
It works for me.
This seems weird, though. The base should have no knowledge of the derived.
Perhaps use static:: instead and rely on overriding static member functions — or "late static binding". You'll need PHP 5.3 for this.
<?php
class Fase {
public static function getbyId($id) {
echo "Fase::getbyId\n";
}
public function getsomefaseitem($fase_item_id) {
static::getbyid($fase_item_id); // <---
}
}
class FaseItem extends Fase {
public static function getbyId($id) {
echo "FaseItem::getbyId\n";
}
}
$f = new Fase();
$f->getsomefaseitem(0);
?>
Related
I am building an MVC component and I'm getting stuck with an issue with a parent and child model. I have a few methods in the parent Model and they're not working with the database_class object
the constructor works fine
but when I use that object in the methods its like the constructor doesn't exist?
Class Controlller
{
public function __construct()
{
$this->childModel = $this->model('childModel');
} // end construct
// methods go here
}
Here are the models:
class childModel extends parentModel {
private $dbo;
public function __construct()
{
$dbobj = new Database_class;
$this->dbo = $dbobj;
}
//methods
}
class parentModel {
private $dbom;
public function __construct()
{
$dbombj = new Database_class;
$this->dbom = $dbombj;
var_dump($this->dbom); //working perfectly as database object
}
public function methodName()
{
var_dump($this->dbom); //not showing up as database object
}
}
I don't think this code is doing what you think it's doing. In childModel, you are overwriting the __construct method of the parentModel, so the __construct in the parentModel never gets called. Therefore $this->dbom should be null. Furthermore if you wish to use $this->dbom from the childModel, you should probably change the scope from private $dbom to protected $dbom. See this page for more info on that: http://php.net/manual/en/language.oop5.visibility.php
here is the class structure. I want Observer:callme() to be callable from Children too.
class Observer
{
protected callme()
{
}
}
class Parent extends Observer
{
function createChild()
{
$this->callme(); // this is OK
return new Child ($this);
}
}
class Child
{
private $this myParent;
public function __constructor ($myParent)
{
$this->myParent = $myParent;
}
public function __destroy()
{
$this->myParent->callme(); // FAIL!
}
}
so how to make FAIL work? (without making it public, because its only for used inside "Parent" and its "Children")
The problem is that a protected method is only accessed from the same class or the class children. What you can do is extend your Child class from Parent, like this:
class Child extends Parent
{
public function __constructor ()
{
parent::__constructor();
}
public function __destroy()
{
$this->callme(); // Should work!
}
}
Or just change the method to public.
And, btw, is this code some kind of real code that you will use? That constructor receiving the parent object seems to be so wrong. What are you trying to accomplish?
protected means that you can call that method only from the same class and from subclasses. What you want to do is not possible. The protected keyword would be pointless if you could call these methods from everywhere.
In C++ there is the friend keyword to achieve what you want: you could define Child as friend of Observer (this has to be done from within Observer), and then you can call all methods in Observer (including private and protected) from within methods of Child. But such a keyword does not exist for PHP.
My comment on your question explains why it doesn't work. This answer shows a way to accomplish what you asked based upon your clarification that MyChild should not extend MyParent.
This is a hack example that makes it work by exploiting the fact that php doesn't care if you call protected methods on other instances than yourself as long as you share the ancestor of the protected method.
I had to change the code some to make it valid php. __constructor is not the name of a php constructor.
hacky.php
<?php
class Observer
{
protected function callme()
{
echo 'I was called from ' . get_called_class(), PHP_EOL;
}
}
class MyParent extends Observer
{
public function createMyChild()
{
$this->callme(); // this is OK
return new MyChild ($this);
}
}
class MyChild extends Observer // hackey extends
{
private $myMyParent;
public function __construct($myMyParent)
{
$this->myMyParent = $myMyParent;
$this->myMyParent->callme();
}
}
$p = new MyParent;
$c = $p->createMyChild();
Result:
$ php hacky.php
I was called from MyParent
I was called from MyParent
I think I found the solution:
class Parent extends Observer
{
function createChild()
{
$this->callme(); // this is OK
return new Child (function() { $this->callme(); });
}
}
class Child
{
private $gatewayFunction;
public function __constructor (Closure $gatewayFunction)
{
$this->gatewayFunction = $gatewayFunction;
}
public function __destroy()
{
$this->gatewayFunction->__invoke();
}
}
Who is going to crap himself? :)
Assume we have the following class (simplified):
class SuperConfig {
public $mainDir;
public function setDir() {
$this->mainDir = "path/to/dir";
}
}
This class is supposed to be extended in EVERY other class in the project, and I do need the setDir() function of the parent to be executed. Obviously, I could do it like this:
class A extends SuperConfig() {
public function __construct() {
parent::setDir();
}
// ... other stuff is about to be done ...
}
and I could access the properties in the child class like this:
class A extends SuperConfig {
public function doSomething() {
SuperConfig::mainDir;
}
}
This is a viable solution, but I got multiple hundreds of classes and doing this in every single one seems tedious. So, is there a way to do something like this:
class SuperConfig {
public $mainDir;
public function __extend() {
$this->setDir();
}
public function setDir() {
$this->mainDir = "path/to/dir";
}
}
__extend() obviously doesn't work like that, but I'm wondering is there is a trick how I could make this work.
class SuperConfig {
public $mainDir;
public function __construct() {
$this->setDir(); // consider moving setDir's code here as well,
// unless you have a good reason for it to be a method
}
public function setDir() {
$this->mainDir = "path/to/dir";
}
}
You simply do this, and then you expect all subclasses to call the parent constructor if they're overriding the constructor:
public function __construct() {
parent::__construct();
// more code
}
It's perfectly reasonable to expect children to call their parent constructor, unless they deliberately want to leave the instance in an unknown and potentially broken state.
Put the constructor in the class that is being extended.
class SuperConfig {
public $mainDir;
public function __construct() {
$this->setDir();
}
public function setDir() {
$this->mainDir = "path/to/dir";
}
}
In any class that extends SuperConfig, if they have a constructor also, be sure to include parent::__construct(); so that setDir is called.
Read deceze's answer for an actual solution to your problem.
I would like to point out tho, that you should not extend every class in your project from a Config class. There are several ways how you could improve that.
1.) Create a static config class which you simply can call everywhere without the need of creation
class SuperConfig {
protected static $mainDir = null;
public static function setMainDir($dir) {
self::$mainDir = $dir;
}
}
2.) Create a trait rather then a parenting class.
trait SuperConfig {
protected $mainDir = null;
public function setMainDir($dir) {
$this->mainDir = $dir;
}
}
which you then can use inside your classes:
class XYZ {
use SuperConfig;
public function doSomething() {
$this->setMainDir('path/to/your/dir/');
}
}
Note that you can do that in the constructor too (which is kinda what you want).
Im not saying those two solutions are the best, but I dont like the thought of extending all classes from a config class. Just does not make much sence. Just imagine that you can only extend from one class per time, while you can use as many traits as you wish (and also have as many static classes as you need).
Well, in this particular case you just need:
class SuperConfig {
public $mainDir = "path/to/dir";
}
A parent class is constructed from outside the child class, thus, it's constructor cannot be called from inside the child. How should one go about accessing properties of the parent from the child in this case.
Example:
class MyParent {
protected $args;
protected $child;
public function MyParent($args=false){
$this->args=$args;
$this->child=new MyChild();
}
public function main(){
$this->child->printArgs();
}
}
class MyChild extends MyParent{
public function MyChild(){}
public function printArgs(){
Echo "args: ".$this->args['key']." = ".$this->args['value']."\n";
}
}
$parent=new MyParent(array('key'=>'value'));
$parent->main();
Empty variables are returned when run:
jgalley#jgalley-debian:~/code/otest$ php run.php
args: =
__construct() is the constructor. You are using a variant from ancient PHP4-times.
You instanciate two completely different objects, therefore of course the property $args is completely independent.
abstract class MyParent {
protected $args;
public function __construct($args=false){
$this->args=$args;
}
public function main(){
$this->printArgs();
}
abstract public function printArgs();
}
class MyChild extends MyParent{
public function printArgs(){
Echo "args: ".$this->args['key']." = ".$this->args['value']."\n";
}
}
$$object=new MyChild(array('key'=>'value'));
$object->main();
This at least works, but a problem is, that I don't know exactly what are the design goals. Because it seems to be a kind of cli-Application you should have a look at existing solutions to get an idea, how it could get solved.
abstract class base {
abstract public function test();
public function run()
{
self::test();
}
}
class son extends base {
public function test()
{
echo 1;
}
}
son::run();
It reports:
Fatal error: Cannot call abstract
method base::test()
But son::test() works,why and is there a way to fix?
"self" is lexically scoped, that is, if you use "self" in a method of Base, "self" means "Base", no matter how you call this method at run time. php5.3 introduced a new kind of dynamic binding, which, ironically enough, is called "static". The following works as expected in php 5.3
abstract class base {
abstract public static function test();
static public function run()
{
static::test();
}
}
class son extends base {
static public function test()
{
echo 1;
}
}
son::run();
Of course:
Fatal error: Cannot call abstract method base::test()
It has no method body you could call. If run() is supposed to be a Template Method, you refer to the class scope with $this instead of self and then create an instance of $son to call run() on it, e.g.
abstract class BaseClass {
abstract public function test();
public function run()
{
$this->test();
}
}
class Son extends BaseClass {
public function test()
{
echo 1;
}
}
$son = new Son;
$son->run(); // 1
which is rather odd, because then you could have just as well called test() directly.
Also note that in your example
son::run();
is wrong, because the run() method is not declared static and while PHP will execute run() nonetheless, it is considered wrong usage and will raise an E_STRICT error. However, if you were to define run() static, you could no longer reference $this, because a static method is not invoked from instance scope, but class scope.
Edit I was about to add the PHP5.3 solution, but see that #erenon already did that, while I was typing, so I only add the appropriate reference in the PHP Manual on Late Static Binding.
Abstract methods do not have an implementation, and thus cannot be called. If the method is not defined as abstract, and actually has an implementation, then it can be executed by your code. For example:
public function test(){
echo "Hello from base!";
}
Factory/singleton pattern mix:
class Base
{
static private $instance;
static function getSon() {
if (null === self::$instance) {
self::$instance = new Son;();
}
return self::$instance;
}
}
class Son
{
public function test() {
echo 1;
}
}
Base::getSon()->test(); //1