RE: [flexcoders] hasEventListener() on null object causes silent failure and exit from block
Yeah, binding can interfere with debugging. I'm sure you already know
this, but for newbies reading this thread...
An exception throws an error which leaves the method immediately and
goes up the stack frame until caught, or until it gets to the top where
the debugger player will show an exceptions dialog and the release
player will simply not execute any more code and let the renderer take a
pass at drawing the display list. The idea behind throwing errors is to
not have to build in code to gracefully work your way up the call stack
when something bad happens. That kind of coding is tricky and requires
that virtually every method return a value.
The recommended pattern, which is required in most strongly-typed
languages is
if (someObj && someObj.someFoo)
Try/catch blocks are more expensive than an additional null check per if
statement. Bracketing entire methods in try/catch is not recommended.
-Alex
From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On
Behalf Of Ben Clinkinbeard
Sent: Wednesday, April 02, 2008 9:58 AM
To: flexcoders@yahoogroups.com
Subject: Re: [flexcoders] hasEventListener() on null object causes
silent failure and exit from block
Ah, yes, binding was involved. I still don't understand why the whole
block exits though. Err, I guess I understand, but I don't like it. :) I
have always wished the null checks worked a bit differently. Like it
would be handy if we could say if( someObj.hasFoo ) and it would just
evaluate to false if someObj was null. Oh well, a boy can dream...
Thanks Alex.
Ben
On Wed, Apr 2, 2008 at 12:53 PM, Alex Harui <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]> > wrote:
I get the RTE when I call greatFun(). Are you sure that wasn't part of
a binding expression evaluation? Those have catch blocks.
From: flexcoders@yahoogroups.com <mailto:flexcoders@yahoogroups.com>
[mailto:flexcoders@yahoogroups.com <mailto:flexcoders@yahoogroups.com> ]
On Behalf Of ben.clinkinbeard
Sent: Wednesday, April 02, 2008 7:25 AM
To: flexcoders@yahoogroups.com <mailto:flexcoders@yahoogroups.com>
Subject: [flexcoders] hasEventListener() on null object causes silent
failure and exit from block
This seems like a bug to me. In the following code if dp is null, the
trace will not be executed.
function greatFun():void
{
if( dp.hasEventListener( "foo" ) )
{
// do stuff
}
trace( "WTF" );
}
It should either throw a RTE or just evaluate to false, shouldn't it?
Thanks,
Ben
Re: [flexcoders] hasEventListener() on null object causes silent failure and exit from block
Ah, yes, binding was involved. I still don't understand why the whole block
exits though. Err, I guess I understand, but I don't like it. :) I have
always wished the null checks worked a bit differently. Like it would be
handy if we could say if( someObj.hasFoo ) and it would just evaluate to
false if someObj was null. Oh well, a boy can dream...
Thanks Alex.
Ben
On Wed, Apr 2, 2008 at 12:53 PM, Alex Harui <[EMAIL PROTECTED]> wrote:
>I get the RTE when I call greatFun(). Are you sure that wasn't part of
> a binding expression evaluation? Those have catch blocks.
>
>
> --
>
> *From:* flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] *On
> Behalf Of *ben.clinkinbeard
> *Sent:* Wednesday, April 02, 2008 7:25 AM
> *To:* flexcoders@yahoogroups.com
> *Subject:* [flexcoders] hasEventListener() on null object causes silent
> failure and exit from block
>
>
>
> This seems like a bug to me. In the following code if dp is null, the
> trace will not be executed.
>
> function greatFun():void
> {
> if( dp.hasEventListener( "foo" ) )
> {
> // do stuff
> }
> trace( "WTF" );
> }
>
> It should either throw a RTE or just evaluate to false, shouldn't it?
>
> Thanks,
> Ben
>
>
>
RE: [flexcoders] hasEventListener() on null object causes silent failure and exit from block
I get the RTE when I call greatFun(). Are you sure that wasn't part of
a binding expression evaluation? Those have catch blocks.
From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On
Behalf Of ben.clinkinbeard
Sent: Wednesday, April 02, 2008 7:25 AM
To: flexcoders@yahoogroups.com
Subject: [flexcoders] hasEventListener() on null object causes silent
failure and exit from block
This seems like a bug to me. In the following code if dp is null, the
trace will not be executed.
function greatFun():void
{
if( dp.hasEventListener( "foo" ) )
{
// do stuff
}
trace( "WTF" );
}
It should either throw a RTE or just evaluate to false, shouldn't it?
Thanks,
Ben
[flexcoders] hasEventListener() on null object causes silent failure and exit from block
This seems like a bug to me. In the following code if dp is null, the
trace will not be executed.
function greatFun():void
{
if( dp.hasEventListener( "foo" ) )
{
// do stuff
}
trace( "WTF" );
}
It should either throw a RTE or just evaluate to false, shouldn't it?
Thanks,
Ben
