Reputation: 10677
This is a very simple question and I feel stupid for asking it, but I am pressed for time and I need to figure it out :)
I just need to know how to make a string that contains text and other variables. For instance in Java I can just do this:
String someString;
for(int i = 0; i>10; i++){
someString = ("this text has printed " + i + " times"); //how do I create this line in C++?
System.out.println(someString);
i++;
}
EDIT 4:
Ok, Rahul G's answer below works pretty good, and the program compiles and ok, but when I run it instead of getting the string I want for the file name, I get a bunch of numbers. For instance: << "frame " << i << " .jpg"
creates: "013679000.jpg" instead of "frame 0.jpg" like I want. Any thoughts?
for(int i = 0; frames; i++)
{
frame = cvQueryFrame(capture);
std::string s = static_cast<std::ostringstream &>(std::ostringstream() << argv[1] << i << " .jpg").str();
cvSaveImage(s.c_str(), frame);
}
Upvotes: 7
Views: 4076
Reputation: 92096
Java:
int i = 5;
double d = 2.23606798;
String s = "Square root of "+i+" is "+d;
C++:
int i = 5;
double d = 2.23606798;
std::ostringstream oss;
oss << "Square root of " << i << " is " << d;
std::string s = oss.str();
// If you need C style string...
char const *s0 = s.c_str();
Please note that the std::ostringstream
class resides in <sstream>
header.
Edit:
Your code (corrected):
for(int i = 0; frames; i++) {
frame = cvQueryFrame(capture);
std::ostringstream oss;
oss << "frame " << i << " .jpg";
cvSaveImage(oss.str().c_str(), frame);
}
Upvotes: 7
Reputation: 11657
There is one more way to do this: use boost::lexical_cast (I know, that it based on std::stringstream, but it pretty useful):
#include <string>
#include <iostream>
#include <boost\lexical_cast.hpp>
int _tmain(int argc, _TCHAR* argv[])
{
int i = 0;
std::string result = "this text has printed " + boost::lexical_cast<std::string, int>(i) + " times";
std::cout<<result<<std::endl;
std::cin.get();
return 0;
}
Upvotes: 3
Reputation:
This is a version of your latest code with your specific function cals removed so I can compile it. It compiles and works:
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main() {
for(int i = 0; i < 10; i++) {
ostringstream os;
os << "frame" << i << " .jpg";
string s = os.str();
cout << s << "\n";
}
}
Upvotes: 0
Reputation: 208446
I posted some code to create strings in place here (basically a wrapper to hide the std::ostringstream
and make calling code cleaner). The usage would be:
void f( std::string const & ); // or std::string, but not std::string&
int var = 5;
f( make_string() << "prefix " << var << " postfix" );
Since you need a const char *
you should use:
void g( const char * );
std::string s = make_string() << "prefix " << var << " postfix";
g( s.str() );
Upvotes: 1
Reputation: 947
How about cvSaveImage(oss.str().c_str(), frame);
? That will make an old C-type zero terminated string which hopefully OpenCV will accept.
Upvotes: 0
Reputation: 10939
If the error you're getting is "error C2664: 'cvSaveImage' : cannot convert parameter 1 from 'std::basic_string<_Elem,_Traits,_Ax>' to 'const char *" then you need a C style string not a C++ one:
cvSaveImage(oss.str().c_str(), frame);
Upvotes: 0
Reputation: 3290
You know you have a bug in your code?? You're incrementing i in the for() statement and at the end of the loop!! But I digress.
Use printf:
printf("This text has printed %d times\n",i)
Hope that helps!
Upvotes: 0
Reputation: 56450
You can use stringstreams for this:
for (int i = 0; i < 10; i++) {
std::ostringstream ss;
ss << "this text has printed " << i << " times";
std::cout << ss.str() << std::endl;
}
Upvotes: 12