Strings passed to a function not altered by it in the D Language

Question

I am a long time C programmer. I have heard about D and have decided to learn it. I like the capabilities it seems to offer. I have come across an issue that has me stumped. I have looked online and haven't found much of an answer. I am trying to pass strings through a function:

module main;

import std.stdio;
import std.string;

int foobar(string s1, string s2)
{
    string t1="Hello";
    string t2="there";
    writeln("t1 = ",t1, " t2 = ", t2);
    s1=t1;
    s2=t2;
   writeln("s1 = ",s1," s2 = ",s2);
   return 0;
}

int main(string[] args)
{
    string a1;
    string a2;
    foobar(a1, a2);
    writeln("a1 = ",a1," a2 = ",a2);
    return 0;
}

The output is as follow:

t1 = Hello t2 = there
s1 = Hello s2 = there
a1 =  a2 = 

I have tried to search online for an answer can I can't find one. I suspect that I am just not asking the right question. I know I can do this using char strings, but I am trying to do this the "D way". Will somebody point me to a reference that can help with this or tell me the question to ask?

If this has been answered before, I apologize. I probably didn't ask the correct question.

Thank you in advance for your time.

Michael

Answer 1

Add ref to your parameters (e.g., int foobar(ref string s1, ref string s2)). A string is just regular slice to immutable chars so it gets passed around by value. If you want to change the slices they needs to be passed by reference.