Question

How can i create a boost::format type formatter object using the character-string or std::string.
Trying to use following code which doesn’t run. Want to achieve code equivalent to following code (semantically):

    format fobj("first-> %1% , second-> %2%");
    std::stringstream s;
    s<<fobj %1 %"%1%.";    //so that I can use s.str() to create a boost object
// How to create fmt object  HERE  
    ss<< fmt %"replacedtext";
    cout<<s.str()<<endl;
    cout<<ss.str();

Sample case:
s should be “first-> 1 , second-> %1%.”
so that I can use this s.str() string to create another format object fmt to which i can feed the substitution values.

Any thoughts folks??

Answer 1

It’s not clear to me what you are trying to do, the boost::format docs are a good place to start, there are a number of clear examples showing how to use the class.

You can create a formatter object and feed elements in via different operations (unlike say, printf where all params need to satisfy the va_arg you pass in).

boost::format fmter("%2% %1%");
fmter % 36; 
fmter % 77;

You can then obtain a string from the result.

std::string s  = fmter.str();

Be aware there are a number of exceptions that can be thrown.

If you are looking for something that dynamically creates a format string you can do that in any number of ways.

std::string strFormatString = "first-> %1% second-> %2%";
boost::format formatter( strFormatString.c_str() );
formatter % value1;
formatter % strFormatString.c_str();
boost::format secondFormatter( formatter.str() );  // etc etc etc