你如何將ac＃abstract class映射到Rust？

Question

可能是措辭不好的問題，但這里舉個例子：

鑒於這些結構;

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

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

這個特點;

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

我如何避免像我一樣重復這些代碼？

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)
    }
}

我有兩次調用相同的函數距離。

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
}

它只是重復的一行代碼，但它可能是更好的例子。 在C＃中，這個代碼將在Waypoint和Poll派生自的抽象類中編寫一次。 什么是慣用的Rust處理這種情況的方式？

Answer 1

通用實現是可能的：

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

但在這種特殊情況下，你應該完全刪除CoordMeasure並在Coord上實現它作為默認方法：

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

您可能還希望把它，以便它可以與其他類型的應對other （我看不出有任何直接的原因， other必須是同一類型self ：

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
}