PHP somo la 53: class inheritance kwenye PHP Object Oriented Programming

Inheritance ni nini?

Hiki ni kitendo kuwa class moja inarithi property na method kutoka class nyingine. Hii inayorithi itaitwa child class yaani class toto. Katika kurithi huku tutazingatia access modifier, hivyo basi tutarithi method na property ambazo ni public au  protected. Class ambayo inayorithi (inherited) huongezewa keyword extends wakati wa kuitengeneza.

Mfano:

<?php

class Gari {

}

class prado extends Gari {

}

?>

Hapo class Gari huitwa parent class na hiyo class prado huitwa child class. Sasa ngoja tuone namna ambavyo tunaweza kurithi method na property ambazo ni public ama protected.

<?php

class Gari

{

   public $jina;

   protected $speed;

   public function __construct($jina, $speed)

   {

       $this->jina = $jina;

       $this->speed = $speed;

   }

   protected function tangazo()

   {

       echo "Tunauza {$this->jina} yenye speed ya {$this->speed}.";

   }

}

class Prado extends Gari

{

   public function tangazo_jipya()

   {

//method tangazo ni protected

       $this->tangazo();

   }

}

$Toyota = new Prado("Toyota", "180 km/h");

$Toyota->tangazo_jipya();

?>

Hapo utaona method tangazo() ni protected lakini tumeweza kuitumia kwenye child class prado(). Hii ni kwa sababu class Prado() imerithi property na method kutoka kwenye parent class  Gari().

Kwa kutumia mfabo huo hata property ikiwa ni protected unaweza kuitumia ndani ya child class bila ya wasi wasi wowote. 

Hapo kuna kitu kipya umekiona {$this->jina} umeona hapo tumetumia mabano {} haya hapo yametumika ili tuweze kutumia hizo property kwenye string. Hii kitaalamu inaitwa string interpolation. Angalia mfano mmoja hapo chini

<?php

$x = 4;

$b = 6;

$z = $x +$b;

echo "jumala ya {$x} na {$b} ni  {$z}";

jumala ya 4 na 6 ni  10

Overriding inherited method

Sasa kuna hii concept hapa tunapasa kuijuwa. Ni kuwa endapo method utaitenegeza upya kwenye child class basi method ya mwanzo itakuwa imebadilishwa. Hapo ndio tunaita overriding method.

Angalia mfa...