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Posted by Jerry Stuckle on 07/17/07 12:16
Yarco wrote:
> Well, friend. Yes, I'm doing PHP. But exception is a traditional
> machinism in programming languages. I'm very doubt about this.
> In procedure language, we return error code when we meet an error. So
> we need to design error code table and judge them in several
> statements. Finally they become boring.
> But how about use exception in OOP? Did we drop all "return error
> code" styles?
> If i want to fetch a webpage:
>
> <?php
> function fetchPage($url)
> {
> //...do something
>
> //if the net speed is very slow, cause we can't fetch the page
> throw new SlowNetSpeed("page can't be getted");
>
> //if the page is moved
> throw new NoPage("page does't exist");
>
> //...do something
> }
>
> // so what can i do, if i want the fetchPage procedure go on fetching
> when SlowNetSpeed Exception happen?
> // it stop when NoPage Exception happen?
> while (1)
> {
> try
> {
> $c = fetchPage('Some_Where');
> // do something
> break;
> }
> catch (SlowNetSpeed $e)
> {
> }
> catch(NoPage $e)
> {
> break;
> }
> }
> ?>
> It is very ugly if there exists more Exceptions and other procedure.
>
> Then i'm missing "return error code" style. But i know "return error
> code" is not a good method when we deal with error. And exception is
> also an ugly grammer when we want to keep code clean.
>
Exceptions originally were designed to handle unexpected conditions,
i.e. connection to a database failed. They really weren't designed to
replace normal error processing (i.e. userid/password mismatch).
Normal errors are generally handled by the calling routine, but
unexpected conditions may be handled by the immediate caller - or
several layers higher. Exceptions give the ability to handle the
condition as high in the calling hierarchy as you need to, without
having to pass return codes from each routine in the which has been called.
I still use them in this way, and it works well.
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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