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Posted by Jerry Stuckle on 11/30/07 02:00
ZeldorBlat wrote:
> On Nov 29, 8:22 pm, bizt <bissa...@yahoo.co.uk> wrote:
>> Hi,
>>
>> Im trying to use a value object class (where a single entity, perhaps
>> from a db, may be represented as an object), for example:
>>
>> class News {
>>
>> private $newsID;
>> private $title;
>> private $description;
>> private $dateAdded;
>>
>> }
>>
>> Now, instead of having to write accessor methods (ie. getNewsID) for
>> each property I am instead using __get and __set to check if an
>> accessor method exists. If one does, use the accessor method otherwise
>> return the value of the private property. See:
>>
>> class News {
>>
>> private $newsID;
>> private $title;
>> private $description;
>> private $dateAdded;
>>
>> public function __get ($propertyName)
>> {
>> if (method_exists ($this, 'get'.$propertyName)) {
>> return call_user_func (array ($this, 'get'.$propertyName));
>> } else {
>> return $this->$propertyName;
>> }
>>
>> }
>>
>> public function __set ($propertyName, $value)
>> {
>> if (method_exists ($this, 'set'.$propertyName)) {
>> return call_user_func (array ($this, 'set'.$propertyName),
>> $value);
>> } else {
>> $this->$propertyName = $value;
>> }
>>
>> }
>> }
>>
>> The above example shows that all properties, altho private, can be
>> treated as public until the time comes that an accessor method is
>> required then on detecting that the accessor method exists, it will
>> refer to that instead. Ofcourse I must stick to the naming convention
>> of 'get[propertyName]' and 'set[propertyName]' which isnt really a
>> problem. Well, thats the theory and so far the above example is
>> working fine but I want to do something slightly different and maybe
>> my understanding of php classes is a little behind.
>>
>> I have a few value objects for various tables and the code for each
>> __get and __set would be the same for each. So, this makes me think
>> that I need to create a parent ValueObject class containing the
>> overload methods (__get __set) and the value object classes (eg. News
>> and the rest) would inherit from ValueObject becoming subclasses of
>> it. See:
>>
>> class ValueObject {
>>
>> public function __get ($propertyName)
>> {
>> if (method_exists ($this, 'get'.$propertyName)) {
>> return call_user_func (array ($this, 'get'.$propertyName));
>> } else {
>> return $this->$propertyName;
>> }
>>
>> }
>>
>> public function __set ($propertyName, $value)
>> {
>> if (method_exists ($this, 'set'.$propertyName)) {
>> return call_user_func (array ($this, 'set'.$propertyName),
>> $value);
>> } else {
>> $this->$propertyName = $value;
>> }
>>
>> }
>> }
>>
>> class News extends ValueObject {
>>
>> private $newsID;
>> private $title;
>> private $description;
>> private $dateAdded;
>>
>> }
>>
>> class Individual extends ValueObject { // another value object
>> .
>> .
>> .
>>
>> This would be ideal as I obviously dont need to keep redeclaring the
>> __get and __set in each VO. However, I get an error when running it
>> this way because $this->$propertyName (well, onscreen it way say News::
>> $newsID if I try to access newsID property) does not exist this time.
>> Is that because it is trying to locate the property in the the
>> ValueObject class? I want each ValueObject subclasses to own the
>> method as though it were writing within its own brackets. Can this be
>> done easily? I have to confess I am new to PHP5 classes so Im hoping
>> that a more experienced PHP programmer may be able to spot where Im
>> going wrong. If someone could point me in the correct direction it
>> would be much appreciated. Thanks
>>
>> Burnsy
>
> What if you declare $newsID, $title, etc. as protected instead of
> private. Private visibility means that the method or property is only
> available from that class. Protected visibility means that it's
> available from anywhere in the inheritance hierarchy.
>
> This code demonstrates that the superclass can access protected
> members of a subclass:
>
> class Superclass {
>
> public function foo() {
> echo $this->bar;
> }
>
> }
>
> class Subclass extends Superclass {
> protected $bar = 'bar';
>
> public function bar() {
> $this->foo();
> }
> }
>
> $c = new Subclass();
> $c->bar();
>
> If I'm misunderstanding your problem let me know.
>
Which is a severe violation of OO principles. What happens, for
instance, if you do:
$c = new Superclass();
$c->foo();
Making Superclass::foo() protected only hides the problem. In true OO
languages, the code in Superclass::foo() would not be allowed (as it
shouldn't be).
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
==================
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