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ЗАДАЧА : Что выведет этот код?


use std::mem;

struct Tracer(&'static str);

impl Tracer {
fn new(name: &'static str) -> Tracer {
println!("Creating {}", name);
Tracer(name)
}
}

impl Drop for Tracer {
fn drop(&mut self) {
println!("Dropping {}", self.0);
}
}

struct Test {
a: Tracer,
b: Tracer,
}

fn main() {
let mut t = Test {
a: Tracer::new("A"),
b: Tracer::new("B"),
};

mem::replace(&mut t.a, Tracer::new("X"));

println!("Midpoint");
}


ОТВЕТ:
```Creating A
Creating B
Creating X
Dropping A
Midpoint
Dropping B
Dropping X
```

1. Создание:
Tracer::new("A") → Creating A
2. mem::replace(...):
Creating X Dropping A
3.
println!("Midpoint"): Midpoint
4. Drop поля:
B, затем X

Этот код демонстрирует поведение Drop при замене полей структуры в Rust через std::mem::replace.


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ЗАДАЧА : Что выведет этот код?


use std::mem;

struct Tracer(&'static str);

impl Tracer {
fn new(name: &'static str) -> Tracer {
println!("Creating {}", name);
Tracer(name)
}
}

impl Drop for Tracer {
fn drop(&mut self) {
println!("Dropping {}", self.0);
}
}

struct Test {
a: Tracer,
b: Tracer,
}

fn main() {
let mut t = Test {
a: Tracer::new("A"),
b: Tracer::new("B"),
};

mem::replace(&mut t.a, Tracer::new("X"));

println!("Midpoint");
}


ОТВЕТ:
```Creating A
Creating B
Creating X
Dropping A
Midpoint
Dropping B
Dropping X
```

1. Создание:
Tracer::new("A") → Creating A
2. mem::replace(...):
Creating X Dropping A
3.
println!("Midpoint"): Midpoint
4. Drop поля:
B, затем X

Этот код демонстрирует поведение Drop при замене полей структуры в Rust через std::mem::replace.


@rust_code

BY Rust


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