Posted by ZeldorBlat on 11/11/07 01:39

On Nov 10, 3:18 pm, Jerry Stuckle <jstuck...@attglobal.net> wrote:
> Oli Thissen wrote:
> > Hello everybody!
>
> > I'm having a little problem with the following: I wrote a class to
> > collect data (Let's call it DataCollector). Now I want the data to be
> > interpreted in various ways. My idea was to write an interface
> > (iVisualizer) so DataCollector could use every user defined
> > (MyVisualizer) class implementing it. Saying "MyVisualizer extends
> > DataCollector" is not an option, since the data should only be
> > collected once and then then being "rendered" by a variety of output
> > classes (to XML, to plain text, to PDF, etc.).
>
> > Here is the code example:
>
> > <php>
> > class DataCollector {
> > private $data
>
> > public function collectData ($someText) {
> > // Write data here
> > }
>
> > public function output($visualizer) {
> > $visualizer->output($this)
> > }
> > }
>
> > class MyVisualizer implements iVisualizer {
> > public function output ($dataCollector)
> > {
> > echo $dataCollector->data;
> > }
> > }
>
> > $a = new DataCollector();
> > $b = new MyVisualizer();
> > $a->collectData("foo");
> > $a->output($b);
> > </php>
>
> > Now, obviously calling "$a->output($b);" will get me in trouble, since
> > DataCollector::data is private. Making DataCollector::data public
> > would make it easy, but also "unsafe". Adding get & set methods will
> > add lots of methods, since $data is just an example for a large number
> > of properties.
>
> > I really hope to get some good ideas here. Thanks in advance!
>
> > Oli
>
> First of all, a Visualizer object is not a "type of" DataCollector, so
> trying to derive Visualizer from DataCollector would be incorrect.
>
> You have the data items are private, as they should be (encapsulation).
> So you need getter and setter methods for each one. The getter
> methods return copies, and the setter methods validate the data before
> actually storing it.
>
> Yes, sometimes it means a bunch of setters and getter methods. But it's
> also the correct way to do it.
>

Everything Jerry said is correct. I would add that, if you have a lot
of private members (i.e. columns from a table in a database) you can
save yourself some work by taking advantage of the __get() and __set()
magic methods:

<http://www.php.net/manual/en/language.oop5.magic.php>

That way you don't need to write individual getters and setters for
every piece of data stored in your object.

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