RUST勉強中、5/29の積み上げ

前回の続き。

anyhowクレートを使用してエラー処理をハンドリングするコードです。

[package]
name = "samplecli"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
clap = { version = "3.1.6", features = ["derive"] }
anyhow = { version = "1.0.57" }

use anyhow::{Context, Result};

fn get_int_from_file() -> Result<i32> {
    let path = "number.txt";

    let num_str = std::fs::read_to_string(path)
        .with_context(|| format!("failed to read string from {}", path))?;

    num_str
        .trim()
        .parse::<i32>()
        .map(|t| t * 2)
        .context("failed to parse string")
}

fn main() {
    match get_int_from_file() {
        Ok(x) => println!("{}", x),
        Err(e) => println!("{}", e),
    }
}