Posted by Jerry Stuckle on 11/10/07 20:18

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.

--
==================
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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