#![allow(dead_code)] // <1> Silence warnings related to FileState::Open not being used
use std::fmt; // <2> Bring the `std::fmt` crate into local scope, allowing us to make use of `fmt::Result`
use std::fmt::{Display}; // <3> Bring `Display` into local scope, avoiding the need for us to prefix it as `fmt::Display` in our code
#[derive(Debug,PartialEq)]
enum FileState {
Open,
Closed,
}
#[derive(Debug)]
struct File {
name: String,
data: Vec<u8>,
state: FileState,
}
impl Display for FileState {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
FileState::Open => write!(f, "OPEN"), // <4> Sneakily, we can make use of `write!` to do the grunt work for us. Strings already implement `Display` themselves, so there's very little left for us to do.
FileState::Closed => write!(f, "CLOSED"), // <4>
}
}
}
impl Display for File {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "<{} ({})>", self.name, self.state) // <5> We can rely on the FileState Display implementation in our own code
}
}
impl File {
fn new(name: &str) -> File {
File {
name: String::from(name),
data: Vec::new(),
state: FileState::Closed
}
}
}
fn main() {
let f5 = File::new("f5.txt");
//...
println!("{:?}", f5); // <1>
println!("{}", f5); // <1>
}
