Question

可能是一个措辞不好的问题，但这里举个例子：

给出这些结构;

pub struct Poll {
    _lat: f64,
    _lon: f64,
    _at: i64,
    _heading: f64,
    _speed: f64,
}

pub struct Waypoint {
    _lat: f64,
    _lon: f64,
}

和这个特性;

pub trait CoordMeasure {
    fn dist_to(&self, other: &Self ) -> f64;
}

如何像我一样避免重复此代码？

impl CoordMeasure for Poll {
    fn dist_to(&self, other: &Poll) -> f64 {
        super::core::distance(self, other)
    }
}

impl CoordMeasure for Waypoint {
    fn dist_to(&self, other: &Waypoint) -> f64 {
        super::core::distance(self, other)
    }
}

我有两次调用相同的函数距离。

pub fn distance<T: Coord>(a: &T, b: &T ) -> f64 {
        let lat1_rads = (90.0 - a.lat()).to_radians();
        let lat2_rads = (90.0 - b.lat()).to_radians();
        let lon_rads = (b.lon() - a.lon()).to_radians();

        let cos_of_lat1 = lat1_rads.cos();
        let cos_of_lat2 = lat2_rads.cos();

        let sin_of_lat1 = lat1_rads.sin();
        let sin_of_lat2 = lat2_rads.sin();

        let cos_of_lons = lon_rads.cos();
        let equation = ((cos_of_lat2 * cos_of_lat1) + (sin_of_lat2 * sin_of_lat1 *    cos_of_lons)).acos();
        6334009.6 * equation
}

它只是重复一行代码，但它可能是一个更好的例子。在C＃中，这个代码将在Waypoint和Poll派生自的抽象类中编写一次。处理这种情况的惯用Rust方法是什么？

Answer 1

通用实现是可能的：

impl<T: Coord> CoordMeasure for T {
    fn dist_to(&self, other: &T) -> f64 {
        super::core::distance(self, other)
    }
}

但在这种特殊情况下，您应该完全删除CoordMeasure并在Coord上将其作为默认方法实现：

trait Coord {
    …
    fn dist_to(&self, other: &Self) -> f64 {
        super::core::distance(self, other)  // or move its contents in here
    }
}

您可能还想制作它以便能够处理其他类型的other（我认为other必须与self必须属于同一类型的任何直接原因：

fn dist_to<Other: Coord>(&self, other: &Other) -> f64 {
    let lat1_rads = (90.0 - self.lat()).to_radians();
    let lat2_rads = (90.0 - other.lat()).to_radians();
    let lon_rads = (b.lon() - self.lon()).to_radians();

    let cos_of_lat1 = lat1_rads.cos();
    let cos_of_lat2 = lat2_rads.cos();

    let sin_of_lat1 = lat1_rads.sin();
    let sin_of_lat2 = lat2_rads.sin();

    let cos_of_lons = lon_rads.cos();
    let equation = ((cos_of_lat2 * cos_of_lat1) + (sin_of_lat2 * sin_of_lat1 *    cos_of_lons)).acos();
    6334009.6 * equation
}

如何将c＃抽象类映射到Rust？

1 个答案: