Edit report at https://bugs.php.net/bug.php?id=46506&edit=1
ID: 46506
User updated by: glideraerobatics at hotmail dot com
Reported by: glideraerobatics at hotmail dot com
Summary: readonly attribute for (public) class variables
Status: Open
Type: Feature/Change Request
-Package: Feature/Change Request
+Package: *General Issues
-PHP Version: 5.3.0alpha2
+PHP Version: 5.4
Block user comment: N
Private report: N
New Comment:
Changed affected PHP version.
Previous Comments:
------------------------------------------------------------------------
[2012-01-24 23:12:32] luke at cywh dot com
I just want the "readonly" keyword to protect a property from being written to
from the outside. I still want to write to the property from within the class.
Here's a simple example of how it could be used:
class Parent
{
readonly public $children = array();
public function addChild($childName)
{
$this->children[] = ucwords(strtolower($childName));
}
}
$parent = new Parent;
$parent->addChild("billy");
$count = count($parent->children); // You can do this
print "Parent has $count children\n";
$name = $parent->children[0]; // You can even do this
print "Parent's first child's name is $name\n";
$parent->children[0] = "BILLY"; // But you can't do this
$parent->children[] = "BOB"; // Or this
$parent->children = NULL; // Or this
unset($parent->children); // Or this
The above example frees you from having to do this:
class Parent
{
protected $children = array();
public function addChild($childName)
{
$this->children[] = ucwords(strtolower($childName));
}
public function hasChild($index)
{
return isset($this->children[$index]);
}
public function getChild($index)
{
return $this->children[$index];
}
public function childCount()
{
return count($this->children);
}
}
I've had to write MANY classes like this. The has/isset, get, and count
functions are virtually all the same.
Some people have even resorted to using __get and __set:
http://stackoverflow.com/questions/402215/php-readonly-properties
The __get and __set magic functions are slow, so much so you're better off
making your own getters and setters, which is multiplied by the number of
properties you need like this in the class.
I would recommend the following definitions:
readonly public = read for public, write for protected
readonly protected = read for protected, write for private
I think this should satisfy most cases.
------------------------------------------------------------------------
[2009-07-12 13:27:08] mickael at lupusmic dot org
I guess the readonly keyword in C# is wrong. It hasn't to disallow variance of the attribute,
but the setting from outside the object. Readonly is opposite to constness of a variable. For
example, DOMDocument::doctype isn't constant.
What you think about, it's a dynamic const attribute, in opposite to static one.
So said, a readonly is like a const attribute, but isn't. And it doesn't deserve a scope
qualifier, it can only be public.
For example :
class thing
{
readonly $status = 'instantiation' ;
public function __construct()
{
// do init stuff
$this->status = 'instantiate' ;
}
public function invalidate()
{
// do stuf
$this->status = 'invalid' ;
}
}
// Usage
$o = new thing ;
echo $o->status ; // display 'instantiation'
$o->status = 'forced' ; // throw an error E_FATAL
$o->invalidate() ; // do stuff then set readonly status attribute
------------------------------------------------------------------------
[2008-11-06 14:11:42] glideraerobatics at hotmail dot com
Description:
------------
Here is a description of this feature in C#:
http://blog.paranoidferret.com/index.php/2007/09/12/csharp-tutorial-the-readonly-keyword/
In a nutshell it allows you to create classes with public variables that are readonly and can only
be written to / initialized by the contructor of the class itself.
This allows the creation of simple objects without having using accessor methods to protect the
internal data that was validated and initialized during construction from corruption.
Note: bug http://bugs.php.net/bug.php?id=39467 is
about a similar problem but the proposed solution is not quite right.
Reproduce code:
---------------
class Person
{
public readonly $name = null;
public readonly $age = null;
public readonly $weight = null;
public function __construct($name, $age, $weight) {
{
if (!isAgeToWeightRatioSane($age, $weight)) {
throw new InvalidArgumentException("Invalid age to weight ratio: $age : $weight");
}
// TODO: other sanity checks here.
$this->name = $name;
$this->age = $age;
$this->weight = $weight;
}
}
$person = new Person('Joe', 22, 100);
$person->age = 33; // throws a yet to be named exception
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=46506&edit=1