Separate method for a single line code? Or embed in the caller function?

I'm having an argument with my boss about whether or not it's better to have a separate function for a single line of code.

The code reads something like:

while (count <= poscount)
{
    key = etc.substr(pos2prev+1, pos-pos2prev-1);
    std::string::iterator end_pos = std::remove(key.begin(), key.end(), ' ');
    key.erase(end_pos, key.end());

    val = etc.substr(pos+1, pos2-pos-1);

    //process key and val
    DEBUG("{\n\t%s:%s\n}\n", key.c_str(), val.c_str());
    json_object_object_add(paramList, key.c_str(), json_object_new_string(val.c_str())); 

    count++;
    pos2prev = pos2;
    pos = etc.find("=", pos+1);
    pos2 = (count == poscount) ? etc.find("\0",pos2+1) : etc.find("&", pos2+1);
}

Is it better coding style to include the line

json_object_object_add(paramList, key.c_str(), json_object_new_string(val.c_str()));

in a separate function name such as processKeyVal(), or leave it as-is?

I'm guessing that your boss's argument is that a well named function would make the code more readable, and I agree with that in general. I often do that myself even when the function contains a single line.

In this particular example I would not bother though. The comment above the json-call says the same thing as the function name would, and there are no obvious advantages to make a function for a single call.

So if your question is specifically for this example, then I agree with you - keep it as it is, but if you want a more general answer, then I agree with your boss.

For example - if this one-liner is something that you use in more than one place, i.e. if calling the "processKeyVal()" function in more than one place makes sense. Then I say you should make a function of it even if it would contain only one line of code.

Or to put it another way - it is not (always) the number of code lines that should determine if you make a separate function of a code snippet.

StackExchange Code Review Q#33434, answer score: 2