如何在模块内部使用const？

Question

我有以下代码：

mod delicious_snacks {
    use self::fruits::PEAR as fruit;
    use self::veggies::CUCUMBER as veggie;

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

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

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

当我尝试打印水果和蔬菜时，我收到一个错误：水果和蔬菜是私有的：

mod delicious_snacks {
    use self::fruits::PEAR as fruit;
    use self::veggies::CUCUMBER as veggie;

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

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

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

任何人都可以向我解释这一点并帮助我解决吗？

Answer 1

定义的项目use的可访问性独立于所用项目的可访问性。这意味着 whilePEAR是公共的，use self::fruits::PEAR as fruit;是私有的。您必须公开导出这些项目：

pub use self::fruits::PEAR as fruit;
pub use self::veggies::CUCUMBER as veggie;

（固定链接到操场）