Rust

❔ 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

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www.tg-me.com/it/Rust/com.rust_code/920

3.2K viewsedited  Apr 19 at 08:47

❔ 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");
}