error1-match.rs

/*
假设我们有个场景：

- 读取一文件
- 将文件内容转化为UTF8格式
- 将转换后格式内容转为u32的数字
 */
fn main() {
    let path = "./dat";
    match read_file(path) {
        Ok(v) => match to_utf8(v.as_bytes()) {
            Ok(u) => match to_u32(u) {
                Ok(t) => {
                    println!("num:{:?}", t);
                }
                Err(e) => {
                    println!("{} {}", path, e)
                }
            },
            Err(e) => {
                println!("{} {}", path, e)
            }
        },
        Err(e) => {
            println!("{} {}", path, e)
        }
    }
}

///读取文件内容
fn read_file(path: &str) -> Result<String, std::io::Error> {
    std::fs::read_to_string(path)
}

/// 转换为utf8内容
fn to_utf8(v: &[u8]) -> Result<&str, std::str::Utf8Error> {
    std::str::from_utf8(v)
}

/// 转化为u32数字
fn to_u32(v: &str) -> Result<u32, std::num::ParseIntError> {
    v.parse::<u32>()
}