// rc1.rs

//
// In this exercise, we want to express the concept of multiple owners via the
// Rc<T> type. This is a model of our solar system - there is a Sun type and
// multiple Planets. The Planets take ownership of the sun, indicating that they
// revolve around the sun.
//
// Make this code compile by using the proper Rc primitives to express that the
// sun has multiple owners.
//
// Execute `rustlings hint rc1` or use the `hint` watch subcommand for a hint.

// I AM NOT DONE

use std::rc::Rc;

#[derive(Debug)]
struct Sun {}

#[derive(Debug)]
enum Planet {
    Mercury(Rc<Sun>),
    Venus(Rc<Sun>),
    Earth(Rc<Sun>),
    Mars(Rc<Sun>),
    Jupiter(Rc<Sun>),
    Saturn(Rc<Sun>),
    Uranus(Rc<Sun>),
    Neptune(Rc<Sun>),
}

impl Planet {
    fn details(&self) {
        println!("Hi from {:?}!", self)
    }
}

fn main() {
    let sun = Rc::new(Sun {});
    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference

    let mercury = Planet::Mercury(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
    mercury.details();

    let venus = Planet::Venus(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
    venus.details();

    let earth = Planet::Earth(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
    earth.details();

    let mars = Planet::Mars(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references
    mars.details();

    let jupiter = Planet::Jupiter(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
    jupiter.details();

    // 使用 Rc::clone 共享同一个 sun，而非创建新的 Sun
    let saturn = Planet::Saturn(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
    saturn.details();

    // 使用 Rc::clone 共享同一个 sun
    let uranus = Planet::Uranus(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
    uranus.details();

    // 使用 Rc::clone 共享同一个 sun
    let neptune = Planet::Neptune(Rc::clone(&sun));
    println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
    neptune.details();

    assert_eq!(Rc::strong_count(&sun), 9);

    drop(neptune);
    println!("reference count = {}", Rc::strong_count(&sun)); // 8 references

    drop(uranus);
    println!("reference count = {}", Rc::strong_count(&sun)); // 7 references

    drop(saturn);
    println!("reference count = {}", Rc::strong_count(&sun)); // 6 references

    drop(jupiter);
    println!("reference count = {}", Rc::strong_count(&sun)); // 5 references

    drop(mars);
    println!("reference count = {}", Rc::strong_count(&sun)); // 4 references

    // 释放 earth，引用计数减为 3
    drop(earth);
    println!("reference count = {}", Rc::strong_count(&sun)); // 3 references

    // 释放 venus，引用计数减为 2
    drop(venus);
    println!("reference count = {}", Rc::strong_count(&sun)); // 2 references

    // 释放 mercury，引用计数减为 1
    drop(mercury);
    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference

    assert_eq!(Rc::strong_count(&sun), 1);
}

Author: unix-dot

exercises/smart_pointers/rc1.rs

@@ -59,18 +59,18 @@ fn main() {
     println!("reference count = {}", Rc::strong_count(&sun)); // 6 references
     jupiter.details();
 
-    // TODO
-    let saturn = Planet::Saturn(Rc::new(Sun {}));
+    // 使用 Rc::clone 共享同一个 sun，而非创建新的 Sun
+    let saturn = Planet::Saturn(Rc::clone(&sun));
     println!("reference count = {}", Rc::strong_count(&sun)); // 7 references
     saturn.details();
 
-    // TODO
-    let uranus = Planet::Uranus(Rc::new(Sun {}));
+    // 使用 Rc::clone 共享同一个 sun
+    let uranus = Planet::Uranus(Rc::clone(&sun));
     println!("reference count = {}", Rc::strong_count(&sun)); // 8 references
     uranus.details();
 
-    // TODO
-    let neptune = Planet::Neptune(Rc::new(Sun {}));
+    // 使用 Rc::clone 共享同一个 sun
+    let neptune = Planet::Neptune(Rc::clone(&sun));
     println!("reference count = {}", Rc::strong_count(&sun)); // 9 references
     neptune.details();
 
@@ -91,13 +91,16 @@ fn main() {
     drop(mars);
     println!("reference count = {}", Rc::strong_count(&sun)); // 4 references
 
-    // TODO
+    // 释放 earth，引用计数减为 3
+    drop(earth);
     println!("reference count = {}", Rc::strong_count(&sun)); // 3 references
 
-    // TODO
+    // 释放 venus，引用计数减为 2
+    drop(venus);
     println!("reference count = {}", Rc::strong_count(&sun)); // 2 references
 
-    // TODO
+    // 释放 mercury，引用计数减为 1
+    drop(mercury);
     println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
 
     assert_eq!(Rc::strong_count(&sun), 1);