Implement Debug trait for large array type

问题:

I gather that Rust provides Debug impl's for arrays size 32 and smaller.

I also gather that I could implement Debug on a larger array by simply using write! with a very long format specifier. But I'm wondering if there's a better way.

What is the recommended method for implementing Debug for an array of length, say, 1024?

回答1:

use std::fmt;

struct Array<T> {
    data: [T; 1024]
}

impl<T: fmt::Debug> fmt::Debug for Array<T> {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        self.data[..].fmt(formatter)
    }
}

fn main() {
    let array = Array { data: [0u8; 1024] };

    println!("{:?}", array);
}

It's not possible to implement Debug for [T; 1024] or some array of a concrete type (ie. [u8; 1024]. Implementing traits from other crates for types from other crates, or implementing a trait from another crate for a generic type, are both not allowed by design,