Debug struct - implement Debug

---

examples/struct/debugging-struct/src/main.rs

use std::fmt;

struct Animal {
    name: String,
    size: String,
    weight: i32,
}

impl std::fmt::Debug for Animal {
    fn fmt(&self, format: &mut fmt::Formatter) -> fmt::Result {
        write!(
            format,
            "Animal {{ name: {}, size: {}, weight: {} }}",
            self.name, self.size, self.weight
        )
    }
}

fn main() {
    let eli = Animal {
        name: String::from("elephant"),
        size: String::from("huge"),
        weight: 100,
    };
    println!("{}", eli.name);
    println!("{}", eli.size);
    println!("{}", eli.weight);

    println!("{:?}", eli);
    dbg!(eli);
}

elephant
huge
100
Animal { name: elephant, size: huge, weight: 100 }
[src/main.rs:23] eli = Animal { name: elephant, size: huge, weight: 100 }