(done) 速通 rustlings(22) 泛型

泛型例子

RUST 中最典型的利用了泛型的例子就是 Vec，它可以装任何数据类型，如下：

// `Vec<T>` is generic over the type `T`. In most cases, the compiler is able to
// infer `T`, for example after pushing a value with a concrete type to the vector.
// But in this exercise, the compiler needs some help through a type annotation.

fn main() {
    // TODO: Fix the compiler error by annotating the type of the vector
    // `Vec<T>`. Choose `T` as some integer type that can be created from
    // `u8` and `i8`.
    let mut numbers = Vec::<i32>::new();

    // Don't change the lines below.
    let n1: u8 = 42;
    numbers.push(n1.into());
    let n2: i8 = -1;
    numbers.push(n2.into());

    println!("{numbers:?}");
}

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泛型实现

以下是我们自己实现泛型的一个例子：

// This powerful wrapper provides the ability to store a value of any type.
// We rewrite it using a generic so that it supports wrapping ANY type `T`.
struct Wrapper<T> {
    value: T,
}

// Adapt the struct's implementation to be generic over the wrapped value.
impl<T> Wrapper<T> {
    fn new(value: T) -> Self {
        Wrapper { value }
    }
}

fn main() {
    // You can optionally experiment here.
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn store_u32_in_wrapper() {
        assert_eq!(Wrapper::new(42).value, 42);
    }

    #[test]
    fn store_str_in_wrapper() {
        assert_eq!(Wrapper::new("Foo").value, "Foo");
    }
}

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