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use std::fs::{Self,File};
use std::io::{Self, Read, ErrorKind};
fn main() {
let greeting_file_result = File::open("hello.txt");
let greeting_file = match greeting_file_result {
Ok(file) => file,
Err(error) => match error.kind() {
ErrorKind::NotFound => match File::create("hello.txt") {
Ok(fc) => fc,
Err(e) => panic!("problem opening file {:?}",e),
},
other_error => {
panic!("problem opening file {:?}",other_error);
}
},
};
// or use unwrap, it will return value or panic just like match
// let greeting_file = File::open("hello.txt").unwrap();
}
// functions to read username from file
// each one is a shorter solution of its previous one.
fn read_username_from_file() -> Result<String, io::Error> {
let username_file_result = File::open("hello.txt");
let username_file = match username_file_result {
Ok(file) => file,
Err(e) => return Err(e),
};
let mut username = String::new();
match username_file.read_to_string(&mut username) {
Ok(_) => Ok(username),
Err(e) => Err(e),
}
}
// ? is like match, but shorter
// return content of Ok() if true, or return Err() from whole function
fn read_username_from_file_short() -> Result<String, io::Error> {
let mut username_file = File::open("hello.txt")?;
let mut username = String::new();
username_file.read_to_string(&mut username)?;
Ok(username)
}
fn read_username_from_file_even_short() -> Result<String, io::Error> {
let mut username = String::new();
File::open("hello.txt")?.read_to_string(&mut username)?;
Ok(username)
}
fn read_username_from_file_shortest() -> Result<String, io::Error> {
fs::read_to_string("hello.txt")
}
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