| Re: An overloading question [message #174495 is a reply to message #174492] |
Tue, 14 June 2011 23:12   |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma:
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Senior Member |
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On 6/14/2011 6:27 PM, sheldonlg wrote:
> On 6/14/2011 2:32 PM, Denis McMahon wrote:
>> On Tue, 14 Jun 2011 12:49:11 -0400, sheldonlg wrote:
>>
>>> I have a problem that I am wrestling with that should be so obvious and
>>> easy -- but it isn't. I have a base class that has a method that calls
>>> another method in the base class with $this->thatOtherMethod. I have
>>> another class that extends the base class and I want to have
>>> thatOtherMethod in the extended class override the one in the base
>>> class. The calling method in the base class is called using and
>>> instance of the extended class pointing to that method.
>>>
>>> Simply, here is an example:
>>>
>>> A.class.php
>>> --------------------------
>>> <?php
>>> abstract class A {
>>> public function b() {
>>> $this->a();
>>> }
>>> protected function a() {
>>> print 'In class A';
>>> }
>>> }
>>> ?>
>>>
>>> B.class.php
>>> ---------------------------
>>> <?php
>>> include_once 'A.class.php';
>>> class B extends A {
>>> public function a() {
>>> print 'In class B';
>>> }
>>> }
>>> ?>
>>>
>>> c.php
>>> ----------------------------
>>> <?php
>>> include 'B.class.php';
>>> $x = new B();
>>> $x->b();
>>> ?>
>>> ----------------------------
>>>
>>> I want it to print out "In class B", but it prints out "In class A".
>>>
>>> I have looked over Google quite a bit and found nothing that helped. I
>>> have tried making the methods public, protected, keep them both the same
>>> access, etc. and have had no luck. Suggestions?
>>
>> I think A->a() is being used as a constructor for the base class when you
>> instantiate the extended class.
>>
>> This might (or might not) be causing confusion as to what's happening.
>>
>> This code:
>>
>> <?php
>>
>> abstract class A {
>>
>> public function x() {
>> print "x() In class A\n";
>> $this->y();
>> }
>>
>> public function y() {
>> print "y() In class A\n";
>> }
>>
>> public function a() {
>> print "a() In class A\n";
>> }
>>
>> }
>>
>> class B extends A {
>>
>> public function y() {
>> print "y() In class B\n";
>> }
>>
>> }
>>
>> print "instantiate\n";
>>
>> $x = new B();
>>
>> print "call function\n";
>>
>> $x->x();
>>
>> ?>
>>
>> gives:
>>
>> instantiate
>> a() In class A
>> call function
>> x() In class A
>> y() In class B
>>
>> Not sure, though, if that solves your problem or not?
>>
>> Rgds
>>
>> Denis McMahon
>
> I modified B to give it an explicit constructor. It still didn't work.
> Why did your example print out that last line. It was never called. Why
> did it use it as a constructor? That doesn't seem to make sense.
>
Unfortunately, PHP doesn't really implement OO constructs very well - in
fact they to a pretty piss poor job of it. One of the problems is with
virtual functions, as you found. A good OO language would work like you
want, but PHP doesn't - the constructor for A will, in this case, only
call a function in A. In C++, Smalltalk, Java and most other OO
languages, you could define y() as virtual and the constructor for A
would call the function y() in B.
But if you created a constructor in B properly, it should call B:y().
I'd suggest checking your code again - you might have made a mistake.
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================
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