function return more than 1 value?

[Anon]

Okay guys
I'm half with you, here is my method, if you can demonstrate using it I'd be in your debt (as if I'm not already Kirk and Vincent)
The pupose is to retrieve the headline,subhead, and text of a given 'page' in the 'article' class.
Below this is an example of the 'setter'/'getter' for the vars.

function get_page($page_count) {

if ($page_count>$this->page_count || $page_count<1) {
	$this->halt("request_page_error");
}
global $headline,$subhead,$text;
$headline=$this->get_headline($page_count);
$subhead=$this->get_subhead($page_count);
$text=$this->get_text($page_count);

}

//***************************************
//heres the methods used above*******

function set_headline($headline) {
$this->headline[$this->page_count]=$headline;
}

function get_headline($page_count) {
return $this->headline[$page_count];
}

Hope its not to confusing and thanks for all your input!

Nick

[Anon]

Hi
I want a function (method) in a class to return a set of vars $a, $b and $c.

Is this a wrong aproach to take?

Nick

[[deleted]]

It depends, do you need it to return three vars? If you do, it's correct. If you don't, you are making a mistake :-)

[kparker]

get_page() is not good because it writes the result, not to the return value, but to global variables. Double-plus-ungood.

If you want it to return an array of values, this is easy:

return list( $this->get_headline($page_count),    $subhead=$this->get_subhead($page_count),
   $text=$this->get_text($page_count) );

[kparker]

To further amplify, what you can do is have the function return an array. And yes, if you need to, it's a good idea. For example, that's how many of the dbms-results functions work: mysql_fetch_row(), pg_fetch_row(), etc.

Also, the calling function can either simply receive the return value as an array, or, if that's not convenient, use list() to gather together a group of scalars, e.g.:

  list($name, $userid, $last_on) = pg_fetch_row( $result, $row_no );

This last is actually a pet peeve of mine: you frequently see people doing unnecessary shuffling of data like this:

  $data = pg_fetch_array( $result );
  $name = $data['name'];
  $userid = $data['userid'];
  $last_on = $data['last_on'];

and then of course $data is never referenced again. :-(

[Anon]

If you really wanted to cut down on 'extraneous' code you could wrap a fetch_row() call in extract.

[kparker]

That's an interesting approach, but it loses the immediacy of rubbing the reader's face in the variable names being used, which I kind of like.

[Anon]

Yep, looks good. How would I retrieve the list of elements?
I've had a nagging feeling about global vars in classes, is this always a bad idea?
I've been doing this a few times this eveneng!

I worked this out a little while ago, it looks similar to your solution but still uses a global var

function get_page($page_count) {

if ($page_count>$this->page_count) {
	$this->halt("request_page_error");
}
global $result;
$result=array($this->get_headline($page_count), $this->get_subhead($page_count), $this-> get_text($page_count));
return $result;

Thanks

Nick

[kparker]

Oops, sorry. Make that

return array(....);

[knickerlas]

Okay,
I got all of that now, one last thing though, I guess it's 'bad practise' to use global vars to write the results of a function/mathod.
Can I return any values known to a function even if they are 'local' to it or should I declare vars 'global' and then 'return' them?

Cheers

Nick

[knickerlas]

I'm trying this but can't retrieve the values?

function get_page($page_count) {

if ($page_count>$this->page_count) {
	$this->halt("request_page_error");
}
return array($headline=$this->get_headline($page_count), $subhead=$this->get_subhead($page_count), $text=$this-> get_text($page_count));

}

nick

[[deleted]]

You should never ever use a function to declare global vars.

The point of a function is that you can call it using a few parameters, and get a result returned from anywhere in your program. If you use global vars, you first have to make sure they are set properly...

[knickerlas]

Thanks for that, I've learned alot about functions over the last 24hrs.

I see your point and will keep my functions 'clean and tidy' but why can you declare them? and why do some of the books I've read demonstrate this?

Cheers

Nick

[[deleted]]

Global vars have their use, but it can get messy quickly, so be carefull.

For example, if you have an online shop, you have scripts that display products.
Ofcourse these products are all in their own categories. The name of this category is something that you'll want to use in allmost all of your scripts for the shop, so you make is a global var, easily accessible in all scripts.

But... now you move on, and create a page where you list products from different categories (like a special-offers page). Now the category changes 5-20 times in one single script. How can you even attempt to know what the original category was before the script started?
And how can you tell which scripts change which vars?
And how can you find out which vars are used by a function?

Usefull but easily messed up.