How do i lock a variable in a class

Durux · 04-20-2008, 06:25 PM

How do i lock a variable in a class so that i can read it but not change it in an instance, without using return.

Class EX:

PHP Code:


			
class MyClass

{

    public $var;

    

    public function ChangeVar(){

        $this->var = rand(1,20);

    }

}

With this i can still change the variable inside the class though.

PHP Code:


			
$class = new MyClass;



$class->ChangeVar();

//But i can also do this, though i don't want to

$class->var = 50;

Is it at all possible to do without using return?

EDIT:
Using PHP5 btw.

Salathe · 04-20-2008, 06:43 PM

Set the visibility to either private or protected. Then to allow reading the value you can use a public method (function) or hook into the __get method.

PHP Code:


			
class MyClass

{

    protected $var;

    

    // ...



    public function getVar()

    {

        return $this->var;

    }

    // or

    public function __get($property)

    {

        if ($property === 'var')

            return $this->var;

    }

}

Durux · 04-20-2008, 08:39 PM

Yes i now that, but the question was if it was possible without using the return command.

Salathe · 04-20-2008, 08:45 PM

Possible, yes. A viable alternative, no.

freenity · 04-20-2008, 09:04 PM

the return is used for reading, you asked about changing it's value?
Well, you can't 'lock' a variable to read only inside a class.
It is supposed that a class is a totally separate entity and you are the one who read/write class's properties unless you don't trust yourself :)

Durux · 04-20-2008, 09:11 PM

Quote:

Originally Posted by freenity

the return is used for reading, you asked about changing it's value?
Well, you can't 'lock' a variable to read only inside a class.
It is supposed that a class is a totally separate entity and you are the one who read/write class's properties unless you don't trust yourself :)

Well i do trust myself, but i just see it as a better solution to be able to 'lock' a variable so only the class and not the instance can give the variable a value.
It would decrease the use of return in a class and you would not need to assign a new variable outside the class to hold the value.