SFML community forums
Help => Graphics => Topic started by: blueeyedlion on June 23, 2011, 08:18:10 pm
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Let's say that I have the integer "x", how do I display its value on the screen?
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Use std::stringstream to convert the variable to std::string then use sf::String (SFML 1.6) / sf::Text (2.0).
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In C++0x, you can also use the function std::to_string().
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Please tell me more of this "C++0x".
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It is the new C++ standard, see the Wikipedia article (http://en.wikipedia.org/wiki/C%2B%2B0x).
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Something like this?
#include <sstream>
#include <string>
...
string hello;
stringstream ss (stringstream::in | stringstream::out);
ss << window.GetInput().GetMouseX();
ss << " ";
ss << window.GetInput().GetMouseY();
hello = ss.str();
sf::Text text(hello);
text.SetPosition(250.f, 450.f);
text.SetColor(sf::Color(255, 255, 255, 170));
window.Draw(text);
...
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Yes, but you are doing it more complicated than necessary.
std::ostringstream ss; // only output stream!
ss << window.GetInput().GetMouseX() << " " << window.GetInput().GetMouseY();
sf::Text text(ss.str());
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Thanks. That is a lot cleaner.
Is it wise to make a global ostringstream and use it multiple times? I guess I also need to clear it after each use.
Or would a function be better. How would I make such a function, the identifier can be int/char or whatever floats.
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Is it wise to make a global ostringstream and use it multiple times? I guess I also need to clear it after each use.
No. Generally, keep variables as local as possible.
Or would a function be better. How would I make such a function, the identifier can be int/char or whatever floats.
I wouldn't write a function, rather a small class with conversion operators, as shown here (http://www.sfml-dev.org/forum/viewtopic.php?p=22019#22019). But sticking to a stringstream object isn't a bad idea, either.
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Ahh, that works gorgeous. Small crit on your code in the other post. For me it only worked when changing str() to string(). :)
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For me it only worked when changing str() to string().
This shouldn't happen. std::stringstream clearly has a member function called str() and not string(). Do you have a macro with this name?
Or could you show a minimal code and the error message?
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Just a note: to 'clear' the stringstream buffer, just do this:
std::ostringstream oss;
// etc
oss.str("");
changing str() to string()
Hmmm. That seems odd. What compiler are you using?
http://cplusplus.com/reference/iostream/ostringstream/str/
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This works as str() returns a reference to the buffer, rather than just its value.
No, str() returns a std::string with the same content as the buffer, i.e. a copy.
str() is just an overloaded function. The overload with a parameter acts as a setter, the one without as a getter.
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Sorry, my mistake. How embarassing - I linked to the documentation and I hadn't even read it properly :oops:
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I get this error:
error C3861: 'str': identifier not found
I have to use this also to make it work:
#include <string>
#include <iostream>
#include <sstream>
using namespace std;
Which suggests that I'm using std::string() instead of str().
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You are almost certainly using it wrong, I have worked with std::stringstream on MSVC 2008 and I have always been calling the member function str(). By the way, you should not overuse using namespace, and completely avoid it in header files.
Can you show a minimal, complete code example with the error?
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You should only have to include <sstream>.
If you are writing oss.string(), then you can't possibly be using std::string.
(Where oss is your std::ostringstream).
But it is definitely str(), anyway.
On the subject of using namespace, IMO it's best to put it in limited scope, for example inside your main function (yes, you can do that ;) ). Then it will only bring stuff in std into scope within main. Of course, sometimes it's easier to put it globally, but that is risky.
@Nexus Beat me to it ^^
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The smallest and worst code where it still works... :P
#include <SFML/Graphics.hpp>
#include <SFML/OpenGL.hpp>
#include <string>
#include <iostream>
#include <sstream>
using namespace std;
class MakeString
{
public:
template <typename T>
MakeString& operator<< (const T& value)
{
mStream << value;
return *this;
}
operator std::string() const
{
return mStream.str();
}
private:
std::ostringstream mStream;
};
int main()
{
sf::RenderWindow window(sf::VideoMode(800, 600), "test", sf::Style::Close);
window.SetFramerateLimit(60);
while (window.IsOpened())
{
// Process events
sf::Event event;
while (window.PollEvent(event))
{
// Close window : exit
if (event.Type == sf::Event::Closed)
window.Close();
// Escape key : exit
if ((event.Type == sf::Event::KeyPressed) && (event.Key.Code == sf::Key::Escape))
window.Close();
}
sf::Text text( string(MakeString() << window.GetInput().GetMouseX() << " " << window.GetInput().GetMouseY() ) );
text.SetPosition(250.f, 450.f);
text.SetColor(sf::Color(255, 255, 255, 170));
window.Draw(text);
window.Display();
}
return 0; //EXIT_SUCCESS
}
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The boost library provides a boost::lexical_cast function that implements this functionality (http://www.boost.org/doc/libs/1_46_1/libs/conversion/lexical_cast.htm).
#include <boost/lexical_cast.hpp>
#include <string>
#include <iostream>
int main()
{
int ntest = 10;
std::string test = boost::lexical_cast<std::string>(test);
std::cout << test << std::endl;
return 0;
}
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So it works there? Then you must have changed something in your actual code. Compare the two and see what you can find.
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Yes works for me, but you guys were wondering why it only worked with string() and not str().
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But you have used str():
return mStream.str();
This is what we were talking about. The point were you have used 'string' below, it is std::string, as it should be, because you are telling the compiler to construct an std::string from a 'MakeString', which it can do by virtue of this function:
operator std::string() const
{
return mStream.str();
}
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hehe, misunderstanding. I was aiming at this part:
Usage:
int main()
{
int health = 100;
sf::String str(MakeString() << "Health: " << health);
}
there I use string() instead of str()
Sorry for wasting time...
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there I use string() instead of str()
I don't see why str is a problem, unless you have a macro called like this.
So, instead of guessing all the time... Either show us a complete code where the error occurs, or let's forget about this ;)
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I've noticed that on some systems/compilers/environments/whatever, you need to include "string.h" and not "string" to get all of its functions. Dont ask me why. Personally I've only came across this using GCC
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Maybe the OP tried to do this:
...
...
sf::Text text( str(MakeString() << window.GetInput().GetMouseX() << " " << window.GetInput().GetMouseY() ) );
...
...
which wouldn't work, and would probably get the "error C3861: 'str': identifier not found"
:)
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I've noticed that on some systems/compilers/environments/whatever, you need to include "string.h" and not "string" to get all of its functions. Dont ask me why. Personally I've only came across this using GCC
<string.h> (aka <cstring>) and <string> are two completely different headers.
<cstring> has things like strcpy, strcmp, etc
<string> has the std::string class