clearing a stringstream

[William Payne]

How do you get rid the contents in a std::stringstream? I'm using one in a
for loop to format some status messages which I print to the screen. The
stringstream member function clear() only clears flags (bits) in the stream,
right? I solved it by declaring the stringstream inside the loop body even
though I have need of another stringstream just after the loop. So for each
iteration the constructor of the stringstream will be executed. Is this how
I should go about it? *looks at sprintf()*

/ WP

 

[John Harrison]

How do you get rid the contents in a std::stringstream? I'm using one in a
for loop to format some status messages which I print to the screen. The
stringstream member function clear() only clears flags (bits) in the stream,

Right.

I solved it by declaring the stringstream inside the loop body even
though I have need of another stringstream just after the loop. So for each
iteration the constructor of the stringstream will be executed. Is this how
I should go about it? *looks at sprintf()*

Do this instead

std::stringstream buf;
....
buf.str(std::string()); // set contents of string stream

john

 

[William Payne]

Do this instead

std::stringstream buf;
...
buf.str(std::string()); // set contents of string stream

john

Thanks John, I will do that instead.

/ WP

 

[Shiju Rajan]

Doesn't flush work for clearing the contents ........stringstream derives
from ostream and this class has a flush function to clear the buffer.

 

[William Payne]

Doesn't flush work for clearing the contents ........stringstream derives
from ostream and this class has a flush function to clear the buffer.

No, everything is still there after a call to flush().

/ WP

 

[John Harrison]

Doesn't flush work for clearing the contents ........stringstream derives
from ostream and this class has a flush function to clear the buffer.

No it doesn't. Flushing the buffer means committing the contents of the
buffer to the final destination. In the case of fstream this means writing
the buffer to a file. But in the case of stringstream the final destination
is the string object held internally in the stringstream object. So flushing
the buffer (if it did anything) would mean writing to the string held
internally in the stringstream object. Its that string that William is
trying to empty, not write to.

john