An inheritance problem/question

[Lefteris]

Hello all. I have had several problems with php inheritance. I am used to the way c++ deals with inheritance so I thought I could inherit constructors somehow. Seems I can't. But my newest problem is this.

I will show you an example of it with the following code:

 

class parent
{
private $other;

public function __construct() { $this->other = new Other(); }

public function doSomething()
{
$this->other->do();
}

}

class child extends parent
{

public function __construct() { $this->other = new Other(); }

public function newFunction()
{
       parent::doSomething();
}
}

 

When I make a new child ... and call the newFunction() I get a:

Fatal error: Cannot access empty property in the line where the parent's doSomething has the other object. Which means it is empty. But why is it empty? Isn't that the same object I am instantiating at the child's constructor? I wanted to make my code a little more neat ... a little more OOP and now I think I just killed my code 

[KevinM1]

Hello all. I have had several problems with php inheritance. I am used to the way c++ deals with inheritance so I thought I could inherit constructors somehow. Seems I can't. But my newest problem is this.

I will show you an example of it with the following code:

 

class parent
{
private $other;

public function __construct() { $this->other = new Other(); }

public function doSomething()
{
$this->other->do();
}

}

class child extends parent
{

public function __construct() { $this->other = new Other(); }

public function newFunction()
{
       parent::doSomething();
}
}

 

When I make a new child ... and call the newFunction() I get a:

Fatal error: Cannot access empty property in the line where the parent's doSomething has the other object. Which means it is empty. But why is it empty? Isn't that the same object I am instantiating at the child's constructor? I wanted to make my code a little more neat ... a little more OOP and now I think I just killed my code 

 

You can inherit the parent constructor.  In fact, PHP does it inherently behind-the-scenes.  Try:

<?php
   class Parent
   {
      private $other;

      public function __construct()
      {
         $this->other = new Other();
      }

      public function doSomething()
      {
         $this->other->do();
      }
   }

   class Child extends Parent
   {
      public function newFunction()
      {
         parent::doSomething();
      }
   }
?>

 

Similarly, if you want to directly invoke the parent constructor, you could always go:

<?php
   public function __construct()
   {
      parent::__construct();
      //additional code if needed
   }
?>

[Lefteris]

Hello and thanks for the reply.

 

I did what you said and just used the constructor it inherited from its parent class but I still get an error at the same line, only this time it is a very different one.

 

Call to a member function do() on a non-object in  ... blah blah

 

Still Following the example code I put it this topic. Any idea why I get this?

[keeB]

Snip from night:

 

<?php
   class Parent
   {
      private $other;

      public function __construct()
      {
         $this->other = new Other();
      }

      public function doSomething()
      {
         $this->other->do();
      }
   }

   class Child extends Parent
   {
      public function newFunction()
      {
         parent::__construct(); # added, works.
         parent::doSomething();
      }
   }
?>