Nested try/catch blocks to give 2 attempts on an operation

[beta2000]

I want to try Refresh() again if the first Refresh() fails. Code:

try
{
try
{
Refresh(); // ... first attempt...
}
catch(...)
{
Refresh(); // ... second attempt...
}
}
catch(...)
{
// Display error message (both attempts failed)
}

My question is -- Is this a good style? Is there a way to not use so
many try/catch and still attempt the operation up to 2 times?

 

[Victor Bazarov]

I want to try Refresh() again if the first Refresh() fails. Code:

try
{
try
{
Refresh(); // ... first attempt...
}
catch(...)
{
Refresh(); // ... second attempt...
}
}
catch(...)
{
// Display error message (both attempts failed)
}

My question is -- Is this a good style? Is there a way to not use so
many try/catch and still attempt the operation up to 2 times?

I think it would be better to have a loop

bool go_on = true;
int attempt = 0, total = 2;

while (go_on) {
try {
Refresh();
go_on = false; // if manages to get here, no need to repeat
}
catch(...) { // whatever you catch
go_on = ++attempt < total;
if (go_on)
do_something_to_set_up_another_attempt(attempt);
}
}

if (attempt == total)
// all attempts failed

That way you can control the number of attempts much easier.

V

 

[red floyd]

I want to try Refresh() again if the first Refresh() fails. Code:

try
{
try
{
Refresh(); // ... first attempt...
}
catch(...)
{
Refresh(); // ... second attempt...
}
}
catch(...)
{
// Display error message (both attempts failed)
}

My question is -- Is this a good style? Is there a way to not use so
many try/catch and still attempt the operation up to 2 times?

You could use a loop. That also allows you easily change the number of
tries.

const int tries = 2;
int j; // deliberately outside the loop
for (j = 0; j < tries ; ++j)
{
try
{
Refresh();
break;
}
catch(...)
{
/* do nothing */
}
}

if (j >= tries)
{
// have a panic attack, all tries failed
}

 

[Alf P. Steinbach]

* (e-mail address removed):

I want to try Refresh() again if the first Refresh() fails. Code:

try
{
try
{
Refresh(); // ... first attempt...
}
catch(...)
{
Refresh(); // ... second attempt...
}
}
catch(...)
{
// Display error message (both attempts failed)
}

My question is -- Is this a good style?

Not in C++.

Is there a way to not use so many try/catch and still attempt
the operation up to 2 times?

void RefreshWithRetry()
{
try{ Refresh(); }
catch( std::exception const& ) { Refresh(); }
}

....
try
{
RefreshWithRetry();
}
catch( std::exception const& x )
{
// Display error message (both attempts failed)
}

If you want a more general solution you could use a loop, and if you want a
still more general solution you could generalize that to a class with the
action performed by a virtual function.

 

[beta2000]

You could use a loop. That also allows you easily change the number of
tries.

const int tries = 2;
int j; // deliberately outside the loop
for (j = 0; j < tries ; ++j)
{
try
{
Refresh();
break;
}
catch(...)
{
/* do nothing */
}
}

if (j >= tries)
{
// have a panic attack, all tries failed
}

Building on this idea, I did something similar (which uses one less
variable )...

int tries = 2;
while ( tries > 0 )
{
try
{
Refresh();
break;
}
catch(...)
{
--tries;
}
}

if ( tries == 0 )
ShowMessage("Error");