Creating Instances From Other Instances With Struct - rust

Question

struct User {
active: bool,
username: String,
email: String,
sign_in_count: u64,
}
fn main() {
let mut user1 = User {
active: true,
username: String::from("someone123"),
email: String::from("someone#example.com"),
sign_in_count: 1,
};
let user2 = User {
active: user1.active,
username: user1.username,
email: String::from("another#example.com"),
sign_in_count: user1.sign_in_count,
};
let user3 = User {
active: user1.active,
username: user1.username, // I got error in this line
email: String::from("another#example.com"),
sign_in_count: user1.sign_in_count,
};
}
I newbie in Rust. I just want to create new struct's instances dependent on user1 instance. but I got this error:
use of moved value: `user1.username`
move occurs because `user1.username` has type `String`, which does not implement the `Copy` traitrustcE0382
main.rs(18, 19): value moved here
how can I fix this?

Answer 1

Strings can't be copied in Rust, they can only be cloned.
When you initialize your struct fields from another struct's fields, Rust tries to either copy or move those fields. It doesn't attempt to clone them.
When you write username: user1.username, you are moving the username out of user1, since it can't be copied. Doing that twice is not allowed. A String can only be owned by one party, and your code attempts make it owned by both user2 and user3.
Here's a working solution that may be a little more concise, too:
#[derive(Clone)]
struct User {
active: bool,
username: String,
email: String,
sign_in_count: u64,
}
fn main() {
let mut user1 = User {
active: true,
username: String::from("someone123"),
email: String::from("someone#example.com"),
sign_in_count: 1,
};
let user2 = User {
email: String::from("another#example.com"),
..user1.clone()
};
let user3 = User {
email: String::from("another#example.com"),
..user1.clone()
};
}
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