Rust解構枚舉

匹配塊可在各種方式析構項目中。
枚舉同樣也可以解構：

// Must derive `Debug` so `println!` can be used.
// `allow` required to silence warnings because only
// one variant is used.
#[allow(dead_code)]
#[derive(Debug)]
enum Color {
// These 3 are specified solely by their name.
Red,
Blue,
Green,
// These likewise tie `u32` tuples to different names: color models.
RGB(u32, u32, u32),
HSV(u32, u32, u32),
HSL(u32, u32, u32),
CMY(u32, u32, u32),
CMYK(u32, u32, u32, u32),
}

fn main() {
let color = Color::RGB(122, 17, 40);
// TODO ^ Try different variants for `color`

println!("What color is it?");
// An \`enum\` can be destructured using a \`match\`.
match color {
    Color::Red   => println!("The color is Red!"),
    Color::Blue  => println!("The color is Blue!"),
    Color::Green => println!("The color is Green!"),
    Color::RGB(r, g, b) =>
        println!("Red: {}, green: {}, and blue: {}!", r, g, b),
    Color::HSV(h, s, v) =>
        println!("Hue: {}, saturation: {}, value: {}!", h, s, v),
    Color::HSL(h, s, l) =>
        println!("Hue: {}, saturation: {}, lightness: {}!", h, s, l),
    Color::CMY(c, m, y) =>
        println!("Cyan: {}, magenta: {}, yellow: {}!", c, m, y),
    Color::CMYK(c, m, y, k) =>
        println!("Cyan: {}, magenta: {}, yellow: {}, key (black): {}!",
            c, m, y, k),
    // Don't need another arm because all variants have been examined
}

}