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Clone

Sometimes you want to make a copy of a value. The Clone trait accomplishes this.

// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0

fn say_hello(name: String) {
    println!("Hello {name}")
}

fn main() {
    let name = String::from("Alice");
    say_hello(name.clone());
    say_hello(name);
}
This slide should take about 2 minutes.

  • The idea of Clone is to make it easy to spot where heap allocations are occurring. Look for .clone() and a few others like vec! or Box::new.

  • It’s common to “clone your way out” of problems with the borrow checker, and return later to try to optimize those clones away.

  • clone generally performs a deep copy of the value, meaning that if you e.g. clone an array, all of the elements of the array are cloned as well.

  • The behavior for clone is user-defined, so it can perform custom cloning logic if needed.