生命周期参数错误:预期1,找到0

Question

我很难在Rust看到指针.此代码将无法编译,因为:wrong number of lifetime parameters: expected 1, found 0 [E0107].那是什么意思？

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)
}

Answer 1

它说你的结构定义包含一个类型参数,因此你的函数也必须创建一个.

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)
}