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rethrowing VCL exceptions

 
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JD
Guest
PostPosted: Fri Jan 30, 2004 10:29 pm    Post subject: Re: rethrowing VCL exceptions Reply with quote


"nicolasr" <nicolasrNOSPAMATSIGNgmx.net> wrote:
Quote:
[...] "You cannot use throw to reraise an exception that was
caught within VCL code"

Your example does not catch an exception thrown by the VCL.
What you wanted to do was something like this which of course
should not work:

try
{
try
{
SomeObject->SomeMethodThatThrowsAnException();
}
catch(const Exception& ex)
{
ShowMessage("Inner catch: " + ex.Message);
throw;
}
}
catch(const Exception& ex)
{
ShowMessage("Outer catch: " + ex.Message);
}

However, you can work around it:

try
{
try
{
SomeObject->SomeMethodThatThrowsAnException();
}
catch( Exception& ex )
{
throw Exception("Inner catch : " + ex.Message);
}
}
catch( Exception& ex )
{
ShowMessage("Outer catch: " + ex.Message);
}

~ JD


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nicolasr
Guest
PostPosted: Fri Jan 30, 2004 11:19 pm    Post subject: rethrowing VCL exceptions Reply with quote


Hi,

while working with VCL exceptions I found the following
in the online help:
"You cannot use throw to reraise an exception that was
caught within VCL code"

I somehow seem to misunderstand what's the point here.
I tried the following code

try
{
try
{
throw Exception("Hello");
}
catch(const Exception& ex)
{
ShowMessage("Inner catch: " + ex.Message);
throw;
}
}
catch(const Exception& ex)
{
ShowMessage("Outer catch: " + ex.Message);
}

which works as I expected.
Could anyone tell me what is meant by the above statement?

thanks,
Nick



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Garfield
Guest
PostPosted: Sat Jan 31, 2004 6:17 am    Post subject: Re: rethrowing VCL exceptions Reply with quote


Hi:
JD is true!
I try it :
//NON VCL
try
{
try
{
throw Exception("Hello");
}
catch(const Exception& ex)
{
ShowMessage("Inner catch: " + ex.Message);
throw;
}
}
catch(const Exception& ex)
{
ShowMessage("Outer catch: " + ex.Message);
}
//Use VCL
try
{
try
{
TListView *lv;
lv->AddItem("",NULL);
}
catch( Exception& ex )
{
throw Exception("Inner catch : " + ex.Message);
}
}
catch( Exception& ex )
{
ShowMessage("Outer catch: " + ex.Message);
}

"JD" <nospam (AT) nospam (DOT) com> дÈëÓʼþ news:401ae8dd$1 (AT) newsgroups (DOT) borland.com...
Quote:

"nicolasr" <nicolasrNOSPAMATSIGNgmx.net> wrote:
[...] "You cannot use throw to reraise an exception that was
caught within VCL code"

Your example does not catch an exception thrown by the VCL.
What you wanted to do was something like this which of course
should not work:

try
{
try
{
SomeObject->SomeMethodThatThrowsAnException();
}
catch(const Exception& ex)
{
ShowMessage("Inner catch: " + ex.Message);
throw;
}
}
catch(const Exception& ex)
{
ShowMessage("Outer catch: " + ex.Message);
}

However, you can work around it:

try
{
try
{
SomeObject->SomeMethodThatThrowsAnException();
}
catch( Exception& ex )
{
throw Exception("Inner catch : " + ex.Message);
}
}
catch( Exception& ex )
{
ShowMessage("Outer catch: " + ex.Message);
}

~ JD




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nicolasr
Guest
PostPosted: Sun Feb 01, 2004 2:26 am    Post subject: Re: rethrowing VCL exceptions Reply with quote
thanks JD and Garfield!
Just in case someone knows: What are the details why I can't
rethrow a VCL exception? When I do it I get an AV, so I assume
it has something to do with the exception object lifetimes?
I can live without knowing the details, would be interesting to know,
though.

thanks for the help,
Nick


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Remy Lebeau (TeamB)
Guest
PostPosted: Sun Feb 01, 2004 5:33 am    Post subject: Re: rethrowing VCL exceptions Reply with quote

"nicolasr" <nicolasrNOSPAMATSIGNgmx.net> wrote


Quote:
Just in case someone knows: What are the details why I
can't rethrow a VCL exception?

Probably has something to do with the fact that it is being originally
thrown by Delphi code, not C++ code. Different languages, different rules.


Gambit



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