C++ C++ Streams String streams
Example
std::ostringstream is a class whose objects look like an output stream (that is, you can write to them via operator<<), but actually store the writing results, and provide them in the form of a stream.
Consider the following short code:
#include <sstream>
#include <string>
using namespace std;
int main()
{
ostringstream ss;
ss << "the answer to everything is " << 42;
const string result = ss.str();
}
The line
ostringstream ss;
creates such an object. This object is first manipulated like a regular stream:
ss << "the answer to everything is " << 42;
Following that, though, the resulting stream can be obtained like this:
const string result = ss.str();
(the string result will be equal to "the answer to everything is 42").
This is mainly useful when we have a class for which stream serialization has been defined, and for which we want a string form. For example, suppose we have some class
class foo
{
// All sort of stuff here.
};
ostream &operator<<(ostream &os, const foo &f);
To get the string representation of a foo object,
foo f;
we could use
ostringstream ss;
ss << f;
const string result = ss.str();
Then result contains the string representation of the foo object.
