shiningthrough

A comparison of Ruby pass by reference and C++ pass by reference

Take the following Ruby and C++ applications:

def do_something(text)
  text = "bar"
end

text = "foo"
do_something(text)
puts text

The Ruby program above outputs "foo"

• Variable "text" holds address of String object containing "foo"
• Call do_something function passing in address of String object containing "foo"
• Address of String object containing "foo" gets copied to local variable "text"
• Local variable "text" then gets the address of newly created String object "bar"
• Local variable "text" goes out of scope
• Variable "text" still holds the address of String object "foo"

#include <iostream>
using namespace std;

void DoSomething (std::string &text)
{
  text = "bar";
}

int main ()
{
  std::string text = "foo";
  DoSomething(text);
  cout << text << "\n";

  return 0
}

The C++ program above outputs "bar"

• Variable "text" holds String object containing "foo"
• Call do_something function passing in address of String object containing "foo"
• Address of String object containing "foo" gets copied to local variable "text"
• String object "foo" is replaced with String object "bar"
• Local variable "text" goes out of scope
• Variable "text" holds String object containing "bar"