Replace part of a string with another string

Question

Is it possible in C++ to replace part of a string with another string?

Basically, I would like to do this:

QString string(\"hello $name\");
string.re         


        

Answer 1

Yes, you can do it, but you have to find the position of the first string with string's find() member, and then replace with it's replace() member.

string s("hello $name");
size_type pos = s.find( "$name" );
if ( pos != string::npos ) {
   s.replace( pos, 5, "somename" );   // 5 = length( $name )
}

If you are planning on using the Standard Library, you should really get hold of a copy of the book The C++ Standard Library which covers all this stuff very well.

Answer 2

I use generally this:

std::string& replace(std::string& s, const std::string& from, const std::string& to)
{
    if(!from.empty())
        for(size_t pos = 0; (pos = s.find(from, pos)) != std::string::npos; pos += to.size())
            s.replace(pos, from.size(), to);
    return s;
}

It repeatedly calls std::string::find() to locate other occurrences of the searched for string until std::string::find() doesn't find anything. Because std::string::find() returns the position of the match we don't have the problem of invalidating iterators.

Answer 3

With C++11 you can use std::regex like so:

#include <regex>
...
std::string string("hello $name");
string = std::regex_replace(string, std::regex("\\$name"), "Somename");

The double backslash is required for escaping an escape character.