Question

你好，我是悦创。

学员答疑：

• https://code.bornforthis.cn/?id=4e72084d-1eaf-44ed-8067-744671491574
• https://code.bornforthis.cn/?id=664ff169-41d6-409f-a05b-02ed42279759

问题代码：

// You can bring module paths into scopes and provide new names for them with
// the `use` and `as` keywords.

#[allow(dead_code)]
mod delicious_snacks {
    // TODO: Add the following two `use` statements after fixing them.
    use self::fruits::PEAR as fruits;
    use self::veggies::CUCUMBER as veggies;

    pub mod fruits {
        pub const PEAR: &str = "Pear";
        pub const APPLE: &str = "Apple";
    }

    pub mod veggies {
        pub const CUCUMBER: &str = "Cucumber";
        pub const CARROT: &str = "Carrot";
    }
}

fn main() {
    println!(
        "favorite snacks: {} and {}",

        delicious_snacks::fruit,
        delicious_snacks::veggie,
    );
}

报错：

D:\LagerA\rust\a-ex\rustlings git:[master]
rustlings run modules2
error[E0425]: cannot find value `fruit` in module `delicious_snacks`
  --> exercises/10_modules/modules2.rs:25:27
   |
11 |         pub const PEAR: &str = "Pear";
   |         ------------------------------ similarly named constant `fruits` defined here
...
25 |         delicious_snacks::fruit,
   |                           ^^^^^ help: a constant with a similar name exists: `fruits`

error[E0425]: cannot find value `veggie` in module `delicious_snacks`
  --> exercises/10_modules/modules2.rs:26:27
   |
16 |         pub const CUCUMBER: &str = "Cucumber";
   |         -------------------------------------- similarly named constant `veggies` defined here
...
26 |         delicious_snacks::veggie,
   |                           ^^^^^^ help: a constant with a similar name exists: `veggies`

warning: unused import: `self::fruits::PEAR as fruits`
 --> exercises/10_modules/modules2.rs:7:9
  |
7 |     use self::fruits::PEAR as fruits;
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: unused import: `self::veggies::CUCUMBER as veggies`
 --> exercises/10_modules/modules2.rs:8:9
  |
8 |     use self::veggies::CUCUMBER as veggies; 
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  

For more information about this error, try `rustc --explain E0425`.
error: could not compile `exercises` (bin "modul
es2") due to 2 previous errors; 2 warnings emitted

Error: Ran exercises/10_modules/modules2.rs with errors

Solution

#[allow(dead_code)]
mod delicious_snacks {
    // 使用 `use` 语句将常量导入到模块的顶层作用域
    pub use self::fruits::PEAR as fruit;
    pub use self::veggies::CUCUMBER as veggie;

    pub mod fruits {
        pub const PEAR: &str = "Pear";
        pub const APPLE: &str = "Apple";
    }

    pub mod veggies {
        pub const CUCUMBER: &str = "Cucumber";
        pub const CARROT: &str = "Carrot";
    }
}

fn main() {
    println!(
        "favorite snacks: {} and {}",
        delicious_snacks::fruit,
        delicious_snacks::veggie,
    );
}