Mutable References

Mutable references are created using &mut instead of & to make the reference. The first variable must be created with mut too. When we make modifications to the reference the value change shows up in the alfa variable too.

The steps for this example are:

  • Create a mutable variable named alfa with a String bound to it
  • Print alfa to display the value
  • Create a variable named bravo that has a mutable reference to alfa
  • Update the value in bravo with .push_str()
  • Print out bravo to display its value
  • Print out alfa again to show that the value updated there too

The output of this code is:

alfa has apple
bravo has applepie
alfa has applepie

SOURCE CODE

fn main() {
  let mut alfa = String::from("apple");
  println!("alfa has {alfa}");

  let bravo = &mut alfa;
  bravo.push_str("pie");

  println!("bravo has {bravo}");
  println!("alfa has {alfa}");
}

CODE RUNNER

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