错误处理

fn main() {
    let age = 18;
    // 使用unwrap() 获取结果,如果结果是Err,则panic
    // let result = do_something(age).unwrap();

    // 使用expect() 获取结果,如果结果是Err,则panic,并给出提示
    // let result = do_something(age).expect("年龄小于18");

    // println!("result: {}", result);

    // 使用match 获取结果
    let result = do_something(age);
    match result {
        Ok(s) => println!("{}", s),
        Err(e) => println!("error: {}", e),
    }
}

fn do_something(age: u8) -> Result<String, String> {
    if age > 18 {
        Ok(String::from("成年"))
    } else {
        Err(String::from("未成年"))
    }
}

fn main() -> Result<(), AppError> {
    let file = File::open("test.txt")?;
    let mut reader = BufReader::new(file);
    let mut line = String::new();
    reader.read_line(&mut line)?;
    println!("{}", line);
    Ok(())
}

enum AppError {
    DatabaseError(String),
    JwtError(String),
    Unauthorized,
    BadRequest(i32),
    IoError(String),
}

impl From<io::Error> for AppError {
    fn from(value: Error) -> Self {
        Self::IoError(format!("IO error: {}", value))
    }
}