Re: php 5 classes: public, protected and private


"Jerry Stuckle" <jstucklex@xxxxxxxxxxxxx> wrote in message
news:bpudnWTDrLPbNPHYnZ2dnUVZ_tudnZ2d@xxxxxxxxxxxxxx
Tony Marston wrote:
"Jerry Stuckle" <jstucklex@xxxxxxxxxxxxx> wrote in message
news:PeudnRKltLJsufHYnZ2dnUVZ_u2dnZ2d@xxxxxxxxxxxxxx

Tony Marston wrote:

"Jerry Stuckle" <jstucklex@xxxxxxxxxxxxx> wrote in message
news:j9-dnQB80fVLOvbYnZ2dnUVZ_rOdnZ2d@xxxxxxxxxxxxxx


Tony Marston wrote:


"Jerry Stuckle" <jstucklex@xxxxxxxxxxxxx> wrote in message
news:Ib6dna_BtYQSifbYnZ2dnUVZ_sSdnZ2d@xxxxxxxxxxxxxx



jopperdepopper wrote:



You should read "can be accessed everywhere".

Private members can be accessed by members of the class only.
Protected members can be accessed by members of the class or a
derived
class.
Public members can be accessed by anyone, including other classes,
functions and any other code.



Thanks Jerry. I'm trying to make a bit of sense of the php 5
approach
to classes, and so far having a hard time. I fail to see the 'why'
behind the 'public, protected and private' and stuff like
abstraction,
interfaces and whatnot.


Intefaces are not necessary in PHP. Once you have defined a method it
is a total waste to time to also define an interface. Interfaces are a
"fix" in those languages as a means of dealing with optional arguments
and statyic typing. PHP has ifferent ways of dealing with bth of
these, therefore interfaces serve no useful purpose.


Ah, the great Tony Marston is back to trolling again.

Wrong. In OO terms, the interface is the way to interact with the
object. It consists of all public members - both methods (functions, in
PHP) and variables. And for derived classes, the base class adds
protected members.

A PHP interface is something entirely different.


I disagree. It is possible to define a function (method) within a class,
then to define a separate thing called an "interface". It is possible
access
the function without using the interface, therefore the interface is not
necessary.


Tony,

You really need to learn about OO before spouting off. In OO terms, an
interface is something entirely different than a PHP interface.


How so? All the documentation I have seen describes how an interface
simply describes a method which it imlements. If it is possible to access
a method (a function in PHP) without going though an interface, ten an
interface is not necessary in any language.


You need to understand the difference between an interface as described in
OO terms and the PHP interface.

The PHP interface defines a set of methods (function) which are required
by the classes which implement the interface. Java is similar in that
respect. But both are a subset of the total interface.

It is possible to access the method directly without an interface, therefore
an interfae is not necessary.


PHP is not the only OO language. Some don't even have a term "interface"
as part of the language. But the still have an interface.

Try some of the books by James Rumbaugh, Grady Booch and/or Ivar
Jacobson.


Feels like things are being over-complicated
somehow... or it's just my being inexperienced on this...

Any other reading material on this suggested, someone?


Look for some good books on OO theory and design.

Two of the concepts in OO are 'encapsulation' and 'methods'.

Encapsulation means the internals of an object are managed only by
that object and are not available to anyone else. In PHP these are
private members.


Wrong. Encapsulation means that the data and the functions which
operate on that data are contained (encapsulated) within a single
object. While the methods (functions) thenselves may be visible the
code behind those methods (i.e. the implementaton behind those
methods) is not. Encapslation is NOT about hiding information, it is
about hiding the implementation. It is not necessary to use
public/private/protected on any methods or properties. It does not add
any functionality, it merely creates restrictions which often get in
the way.


Wrong again, Tony. Encapsulation means internal representations of the
object are not visible outside of the class. Just like the base &
mantissa are not visible outside of a floating point number.


I disagree. Encapsulation means that both the data and the methods which
operate on that data are contained within a single unit or "capsule".
The data names and the method names may be visible, it is only the code
which lies behind each method name which is invisible. A piece of data
may be accessed directly, as in $object->var, or it may be accessed
through a getter, as in $object->getVar().

If you bothered to read the right books you will see that encapsulation
means "implementation hiding" and not "information hiding".


Again, read the experts before spouting off. You have repeatedly shown
how little you understand about OO programming techniques.

And yes, encapsulation is "implementation hiding". And the variables are
part of the IMPLEMENTATION.


I disagree. Inplementation is code, information is data. If you don't
believe me then read "Encapsulation is not information hiding" at
http://www.javaworld.com/javaworld/jw-05-2001/jw-0518-encapsulation.html
and also "Abstraction, Encapsulation, and Information Hiding" at
http://www.itmweb.com/essay550.htm


OK, so you quote a couple of blogs by people who have their own opinions.

Read books by the authors I mentioned. They are the experts on OO, not
just anyone who can post a blog or essay on the web.

Oh, I see. Only those people who agree with you can be called experts, while
everyone else is a charlatan. Even Martin Fowler says that "Encapsulation
Wasn't Meant To Mean Data Hiding" at
http://homepage.mac.com/keithray/blog/2006/02/22/, so are you saying that
Martin Fowler is not an expert?



Methods are implemented as functions in PHP. They operate on the
object.


That's one thing you got right.


More than you got right. Go crawl back into your hole and don't come
out again until you know what you're talking about.


I do know what I'm talking about..


Then why do you continually disagree with the recognized experts in the
OO community, like the ones I mentioned above?


I disagree with YOU simply because you clam to be a recognised expert
when in fact you are no such thing. I keep finding papers on the internet
which disagree with your explanations, yet you persist in claiming that
you are right and everybody who dares to disagree with you is wrong. Such
arrogance!


No, you disagree with every recognized expert in the field. Read what the
authors I mentioned have to say about it. THEY are the recognized experts
in the field.

There is no such thing as a single view upon which all "experts" agree.
Wherever you look, either in books or on the internet, you will come across
examples where different sets of "experts" have different opinions and
views. Therefore it does not matter which set of "experts" you choose to
follow as a different set of "experts" will always say that you are wrong.

I can create a paper on the internet saying the sun rises in the west.
It's quite simple to do. But that doesn't make it a fact.

In your opinion it does if an "expert" says so. You have to know when an
"expert" is spouting wisdom and when he is spouting bulls*t.

Now go home and do some reading. You might actually learn something.

The only thing I can learn from you is how NOT to do things.

--
Tony Marston
http://www.tonymarston.net
http://www.radicore.org


.

Relevant Pages

  • Re: php 5 classes: public, protected and private
    ... Private members can be accessed by members of the class only. ... Intefaces are not necessary in PHP. ... Once you have defined a method it is a total waste to time to also define an interface. ... Encapsulation means the internals of an object are managed only by that object and are not available to anyone else. ...
    (comp.lang.php)
  • Re: php 5 classes: public, protected and private
    ... Private members can be accessed by members of the class only. ... Intefaces are not necessary in PHP. ... Once you have defined a method it is a total waste to time to also define an interface. ... Encapsulation means the internals of an object are managed only by that object and are not available to anyone else. ...
    (comp.lang.php)
  • Re: php 5 classes: public, protected and private
    ... Private members can be accessed by members of the class only. ... Intefaces are not necessary in PHP. ... the interface is the way to interact with the ... Two of the concepts in OO are 'encapsulation' and 'methods'. ...
    (comp.lang.php)
  • Re: php 5 classes: public, protected and private
    ... Private members can be accessed by members of the class only. ... Intefaces are not necessary in PHP. ... Once you have defined a method it is a total waste to time to also define an interface. ... Encapsulation means the internals of an object are managed only by that object and are not available to anyone else. ...
    (comp.lang.php)
  • Re: php 5 classes: public, protected and private
    ... Private members can be accessed by members of the class only. ... Intefaces are not necessary in PHP. ... Interfaces are a "fix" in those languages as a means of dealing with optional arguments and statyic typing. ... Encapsulation means the internals of an object are managed only by that object and are not available to anyone else. ...
    (comp.lang.php)