How to unpack a struct in another struct in rust?

Can you do something like this?

struct Person {
hp: i32
}

struct EvolvedPerson开发者_运维技巧 {
hp: i32,
evolved_stat: i32,
}

let p1 = Person { hp: 10 }
let p2 = EvolvedPerson { ..p1, extra_stat: 20 }

Where the p2 now has the hp of p1.

---

Can you do something like this?

No. You can only unpack structs of the same type.

---

As a possible solution you can deconstruct p1 and then provide variables to p2 by shorter syntax:

struct Person {
    hp: i32
}

struct EvolvedPerson {
    hp: i32,
    evolved_stat: i32,
}

let p1 = Person { hp: 10 };

let p2 = {
    let Person { hp } = p1;
    EvolvedPerson { hp, extra_stat: 20 }
};

---

The idiomatic way would be to include the Person struct instead:

struct Person {
    hp: i32,
}

struct EvolvedPerson {
    person: Person,
    evolved_stat: i32,
}

let p1 = Person { hp: 10 }
let p2 = EvolvedPerson { person: p1, extra_stat: 20 }

That way it is also trivial to implement AsRef<Person> for EvolvedPerson and thus you can use Person methods with EvolvedPerson too.