PHP How to refer to a class method definition? - php

Question

I would like to bind a function (a method of a class) to another class. Any idea of how i could achieve this?
Here is an example of what i want:
class A {
protected $prop = "prop A";
function method($arg1, ...) {
return $this->prop;
}
}
class B {
protected $prop = "prop B";
// need help here
}
So i want to "bind" the method "method" of class "A" to class "B" so it'll be possible to do $b = new B(); $b->method($arg1, ...); and obtain "prop B";
Thanks in advance!!
I tried:
class B {
protected $instance;
protected $prop = "prop B";
public function __construct($instance) {
$this->instance = $instance;
}
public function __call($method, $args) {
return call_user_func_array([$this->instance, $method], $args);
}
}
$b = new B(new A());
$b->method();
But still outputing "prop A";
I tried this too:
class B {
protected $prop = "prop B";
public function __call($method, $args) {
return call_user_func_array(Closure::bind($this->$method, $this, get_called_class()), $arguments);
}
}
$a = new A();
$b = new B();
$b->method = $a->method;
$b->method();
But i'm getting this error: Closure::bind() expects parameter 1 to be Closure, null given....
At last i tried this too:
class B {
protected $instance;
protected $prop = "prop B";
public function __construct($instance) {
$this->instance = $instance;
}
public function __call($method, $args) {
$new_method = $this->instance->$method->bindTo($this);
return call_user_func_array($new_method, $args);
}
}
$b = new B(new A());
$b->method();
Here, an error says $this->instance->$method is null

Answer 1

Using dependency injection, you can access the passed object:
class A {
public function speak() { return ‘meow’; }
}
class B {
public function __construct($obj) {
$this->a = $obj;
}
}
$demo = new B( new A));
print $demo->a->speak();
// => meow
From here, if you want B->speak to refer to A->speak:
class A {
public function speak() { return ‘meow’; }
}
class B {
public function __construct($obj) {
$this->a = $obj;
}
public function speak() {
return $this->a->speak();
}
}
$demo = new B( new A));
print $demo->a->speak(); // meow
print $demo->speak(); // meow
Or, if B is a special kind of A:
// use obj A above
class B extends A {
// do stuff B knows
}
$demo = new B;
print $demo->speak();
// => meow
If you’re wanting the exact same method in both classes, perhaps what you’re looking for is traits. Traits are more or less an include for objects which lets objects “share” code. (Personally I think it’s a fancy way of violating DRY and is better handled with DI... but smarter people than I have included it in the language)
Using traits would be something like this (double check docs, I’ve never used this)
trait sharedMethod {
public function speak() {
return $this->prop;
}
}
class A {
use sharedMethod;
public $prop = “I’m from A”;
}
class B {
use sharedMethod;
public $prop = “I’m from B”;
public function __construct(object $a) {
$this->a = $a;
}
/**
* use this to get A’s method, or omit to keep B’s method
*/
public function speak() {
return $this->a->speak();
}
}
$demo = new B( new A));
print $demo->speak(); // I’m from A
// if you don’t override the method
$demo = new B( new A));
print $demo->speak(); // I’m from B