详解Rust语言中anyhow的使用

[dependencies]
anyhow = "1.0"

use anyhow::Result;

// 使用标准库的 Result
fn do_something() -> Result<(), std::io::Error> {
    //...
    Ok(())
}
// 使用 anyhow::Result
fn do_something_anyhow() -> anyhow::Result<()> {
    //...
    Ok(())
}

use anyhow::anyhow;
let err = anyhow!("Something went wrong");

use anyhow::Error;
fn from_io_error(io_err: std::io::Error) -> Error {
    io_err.into()
}

use anyhow::{Context, Result};
fn read_file(path: &str) -> Result<String> {
    std::fs::read_to_string(path).with_context(|| format!("Failed to read file at {}", path))
}

fn main() -> anyhow::Result<()> {
    let content = read_file("path/to/file")?;
    println!("{}", content);
    Ok(())
}

if let Some(io_err) = err.downcast_ref::<std::io::Error>() {
    // Handle std::io::Error
}

// 定义一个自定义错误类型
#[derive(thiserror::Error, Debug)]
enum MyError {
    #[error("failed to read string")]
    ReadError(#[from] std::io::Error),
}
// 使用anyhow::Result
fn do_something() -> anyhow::Result<()> {
    let _: Result<String, MyError> = Err(MyError::ReadError(std::io::Error::new(std::io::ErrorKind::Other, "oh no!")));
    // ...
    Ok(())
}

fn main() -> anyhow::Result<()> {
    let path = "some_path.txt";
    let content = std::fs::read_to_string(path).with_context(|| format!("Failed to read file at {}", path))?;
    println!("File content: {}", content);
    Ok(())
}