Using string and stringstream effectively

**leeor_net** · 07-13-2009

I've been scratching my head over this one for a bit. I've looked around and various references, articles, tutorials, etc. but I can't seem to find an effective solution.

I'm outputting a series of information using stringstreams to easily generate strings with number values. Simple enough. I can't seem to get the stringstream cleared so I can use it again for a new operation. This is the code that I have and I just know that there's a more effective way to handle this:

Code:

stringstream tmpStr, tmpStr2;
tmpStr << "Some data";
tmpStr2 << "Some data 2";

drawText(mTestFont, tmpStr.str().c_str(), 0, 0);
drawText(mTestFont, tmpStr2.str().c_str(), 0, 20);

Declaring a new stringstream object every time I want a new bit of information can't possibly be an effective way of doing this and it looks truly ridiculous when I have 10 or 12 different strings I'm trying to output in the same function. Not to mention the maintenance headache.

I've tried using the clear() and seekg(0, ios::beg) functions but haven't had any luck. I simply end up with the original string with the string tacked onto the end of it.

What's the appropriate way to properly clear/flush a string stream so that I can use it again with a 'blank slate' so to speak?

Thanks.

**laserlight** · 07-13-2009

Originally Posted by leeor_net

What's the appropriate way to properly clear/flush a string stream so that I can use it again with a 'blank slate' so to speak?

I believe it should be:

Code:

tmpStr.str("");

You may need to use the clear() member function as well to clear say, an EOF state if you had used the stringstream as an output stream.

You might also want to consider the use of Boost.Format, depending on your requirements.

**leeor_net** · 07-13-2009

Thanks, laserlight. As always, a prompt, consise answer without lessons in 'coding ettiquette'. I figured it had to be something as simple as that.

Thank you!

**Elysia** · 07-13-2009

You might also consider boost::lexical_cast for conversions, along with Boost.Format. Handy stuff.

**execute** · 07-13-2009

You know I always seem to use strings instead, never had a need to use stringstream except in special cases, especially conversions. Perhaps if you keep having to reuse a stringstream might as well try using just strings?

**laserlight** · 07-13-2009

Originally Posted by execute

You know I always seem to use strings instead, never had a need to use stringstream except in special cases, especially conversions. Perhaps if you keep having to reuse a stringstream might as well try using just strings?

I agree: in the given example, the use of a string will suffice, and a stringstream is unnecessary complication. However, leeor_net mentioned "using stringstreams to easily generate strings with number values", and presumably the actual code is something like this:

Code:

for (int i = 0; i < n; ++i)
{
    stringstream ss;
    ss << "Some data " << n;
    drawText(mTestFont, ss.str().c_str(), 0, 0);
}

A stringstream would actually be useful in such a case, as demonstrated.

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