生命周期参数数量错误:预期为 1，发现为 0

问题描述

我很难理解 Rust 中的指针.此代码无法编译，因为:生命周期参数的数量错误:预期为 1，找到 0 [E0107].这是什么意思?

I'm having a really hard time fathoming pointers in Rust. This code won't compile because: wrong number of lifetime parameters: expected 1, found 0 [E0107]. What does that mean?

struct Planet<'a> {
    name: &'a str,
    radius_km: i32,
    surface_area_km2: i64,
    orbital_period_days: i32,
    distance_from_sun: i64
}

fn mercury() -> Planet {
    Planet {
        name: "Mercury",
        radius_km: 2_440,
        surface_area_km2: 74_800_000,
        orbital_period_days: 88,
        distance_from_sun: 57_910_000
    }
}

fn main() {
    let mercury = Box::new(mercury());
    println!("{}",mercury.name)
}

推荐答案

这意味着您对结构的定义包括一个类型参数，因此，您的函数也必须创建一个类型参数.

It's saying that your definition for the struct includes a type parameter and, therefore, so must your function that creates one.

struct Planet<'a>{
    name : &'a str,
    radius_km: i32,
    surface_area_km2: i64,
    orbital_period_days: i32,
    distance_from_sun: i64
}

fn mercury<'a>()->Planet<'a>{
    Planet{
        name:"Mercudy",
        radius_km: 2_440,
        surface_area_km2: 74_800_000,
        orbital_period_days: 88,
        distance_from_sun: 57_910_000
    }
}

fn main(){
    let planet = mercury();
    println!("{}", planet.name)
}

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