如何使用stringstream将int分配给字符串？

Question

How do I assign an int to a string with stringstream ?

The " stringstream(mystr2) << b; " doesn't assign b to mystr2 in the example below:

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main()
{
    string mystr = "1204";
    int a;
    stringstream(mystr) >> a;
    cout << a << endl; // prints 1204

    int b = 10;
    string mystr2;
    stringstream(mystr2) << b;
    cout << mystr2 << endl; // prints nothing
    return 0;
}

Answer 1

This should do:

stringstream ss;
ss << a;
ss >> mystr;

ss.clear();
ss << b;
ss >> mystr2;

Answer 2

int b = 10;
string mystr2;
stringstream ss;
ss << b;
cout << ss.str() << endl; // prints 10

Answer 3

This will print out the '10' correctly below.

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main()
{
    string mystr = "1204";
    int a;
    stringstream(mystr) >> a;
    cout << a << endl; // prints 1204

    int b = 10;
    string mystr2;
    stringstream ss;
    ss << b;
    ss >> mystr2;
    cout << mystr2 << endl; // prints 10
    return 0;
}

Answer 4

When you create a string stream with the ctor stringstream(mystr2) the mystr2 is copied as the initial content of the buffer. mystr2 is not modified by subsequent operations on the stream.

To get the content of the stream you can use the str method:

int b = 10;
string mystr2;
stringstream ss = stringstream(mystr2);  
ss << b;
cout << mystr2.str() << endl; 

See constructor and str method.

Answer 5

The answer to your literal question is:

int b = 10;
std::string mystr2 = static_cast<stringstream &>(stringstream()<<b).str();
cout << mystr2 << endl;