extend a function in a class

fxpepper

Hello,

What is the best way to do this...extend the class and override a function? Or can i just override the function without extending the class?

Also, it's a long function, is it possible to call what's already there and just add my short addition (which is just echoing a few details).

does that makes sense?

thanks

laserlight

It depends. Maybe just writing a non-member function is the best approach. Maybe the class is designed according to the Template Method pattern, and the solution is to extend the class and override a different member function that is called from this one.

fxpepper

just another though...

maybe it's best to just add a new function to this class that adds this echo statement...but the first class is already instantiated on this page...so would i leave that and just add this extended class but just call this new function. is that possible?

thanks again

laserlight

fxpepper wrote:
maybe it's best to just add a new function to this class that adds this echo statement...but the first class is already instantiated on this page...so would i leave that and just add this extended class but just call this new function. is that possible?

It is trivially possible.

If you want an evaluation on what is "best", then you need to provide the scenario and context. What are you trying to do? What is this class? Is this class part of a hierarchy? What is this function? What do you want to do differently concerning this function?

fxpepper

laserlight;10995605 wrote:
It is trivially possible.

If you want an evaluation on what is "best", then you need to provide the scenario and context. What are you trying to do? What is this class? Is this class part of a hierarchy? What is this function? What do you want to do differently concerning this function?

Well i have a class that creates a form. I need to add a function that prints/echoes out information as the originally class doesn't do this. But I do need the information from this original class.

does that help?

thanks again

laserlight

fxpepper wrote:
Well i have a class that creates a form. I need to add a function that prints/echoes out information as the originally class doesn't do this. But I do need the information from this original class.

It sounds like all you need to do is to write a function, e.g.,

function foo($x)
{
    $x->foo();
    echo "information";
}

That is, subclassing is overkill. However, if you already have code that is using this class, and you want to introduce new behaviour into existing code without changing the code itself while retaining the option of the current behaviour, then subclassing makes sense.

bradgrafelman

Just thought I'd throw another point of view out there (especially with laserlight talking about changing/refactoring existing code)...

fxpepper;10995600 wrote:
Also, it's a long function

Perhaps that's one of the problems - it's too long? In other words, is the method's name just a word or two, and does that method stick to its name and do only what that name says it does?

There was a similar issue here on the board some time ago; the "problem" was reportedly with the person's connect() method, but as it turns out that was a bad name for that particular method; a better name would have been connectWithoutVerifyingAndThenSelectDBAndThenExecuteAQuery(). Notice the problem? The solution was to break out the different actions going on inside there into multiple (relatively more) "singular" methods.

Again, it all depends on exactly what it is you're trying to do.

fxpepper

laserlight;10995609 wrote:
It sounds like all you need to do is to write a function, e.g.,
function foo($x)
{
    $x->foo();
    echo "information";
}
That is, subclassing is overkill. However, if you already have code that is using this class, and you want to introduce new behaviour into existing code without changing the code itself while retaining the option of the current behaviour, then subclassing makes sense.

So i set this up but now how would I call this?

when I did this:

foo();

after the above, I get the following response:
"Warning: Missing argument 1 for foo(), called in /var/www/test-file.php on line 45 and defined in /var/www/test-file.php on line 40

Fatal error: Call to a member function foo() on a non-object..."

or is the function/method itself supposed to do that. When I don't call the function (outside of the function), nothing happens...

thanks for all the help!

bradgrafelman

Look at the function definition - it expects a parameter to be passed in (namely an object) and yet it never verifies that it received a valid argument. Thus, it transfers that responsibility onto the caller, and yet you're not passing any parameters at all when you call the function.

fxpepper

bradgrafelman;10995613 wrote:
Just thought I'd throw another point of view out there (especially with laserlight talking about changing/refactoring existing code)...
Perhaps that's one of the problems - it's too long? In other words, is the method's name just a word or two, and does that method stick to its name and do only what that name says it does?

There was a similar issue here on the board some time ago; the "problem" was reportedly with the person's connect() method, but as it turns out that was a bad name for that particular method; a better name would have been connectWithoutVerifyingAndThenSelectDBAndThenExecuteAQuery(). Notice the problem? The solution was to break out the different actions going on inside there into multiple (relatively more) "singular" methods.

Again, it all depends on exactly what it is you're trying to do.

well, it's not that long but my point was that I just wanted to add a little bit of extra code-and attach it to this function. And it probably should be separate from that - you're right in that way - since it does something a little bit different.

thanks!

fxpepper

bradgrafelman;10995618 wrote:
Look at the function definition - it expects a parameter to be passed in (namely an object) and yet it never verifies that it received a valid argument. Thus, it transfers that responsibility onto the caller, and yet you're not passing any parameters at all when you call the function.

okay, I see...so now i have this:

function echo_results($x)
{
    $x->echo_results();
    echo "information";
}

and now trying this:

echo_results($x);

I am still getting the following error:

"Call to undefined method object_class::echo_results() in /var/www/test-file.php on line..."

thanks again -in advance.

bradgrafelman

As the error message states, there is no 'echo_results' method in the class 'object_class'.

fxpepper

bradgrafelman;10995632 wrote:
As the error message states, there is no 'echo_results' method in the class 'object_class'.

Right...
I am obviously a little confused here. can you help or direct me?

bradgrafelman

Well not really, no, because a) I don't know what class you're actually using (I'm assuming 'object_class' is a placeholder... but even if it wasn't, you've never shown us a class definition for 'object_class' either), and b) I don't know which method within that (unknown) class you're trying to call.

niroshan

Hi fxpepper,

I think you misunderstood laserlight`s solution. He was telling this,

class foo
{
	private $formdata;

function generateForm()
{
	$this->formdata = 'This is the form data';
	echo $this->formdata;	
}	
}

function displayAdditionalData($obj)
{
	$obj->generateForm();

echo "<br />information"; 
}

$fooObj = new foo();

displayAdditionalData($fooObj);

The problem with your question is you never explain us what you need to do.

Well i have a class that creates a form. I need to add a function that prints/echoes out information as the originally class doesn't do this. But I do need the information from this original class.

What kind of information you need?

If you provide us with more information we can surely help you out.

Thanks,
best regards,
Niroshan