2022年04月15日 日更 102 / 100 天

大家好，我是明哥。为什么我要坚持输出读书笔记，因为我想看看自己的这场实验，到最后会有什么收获。

上一次我们学了Rust 代码使用测试驱动开发的思路，完善代码逻辑。这一次我们学习或许环境变量的配置，然后调用不同的函数方法。

01

编写一个大小写不敏感的 search 函数的不通过的测试

use std::{error::Error, fs};

pub struct Config { // 结构体、及属性；方法都需要使用 pub 改造
    // 使用结构体组合参数使之有意义
    pub query: String,
    pub filename: String,
}

impl Config {
    pub fn new(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }
        let query = args[1].clone();
        let filename = args[2].clone();
        Ok(Config { query, filename })
    }
}

pub fn run(config: Config)-> Result<(), Box<dyn Error>> {
    let content =
    fs::read_to_string(config.filename)?;

    for line in search(&config.query, &content) {
        println!("{}", line);
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let content = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape";

        assert_eq!(vec!["safe, fast, productive."], search(query, content));
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
        Rust:
        safe, fast, productive.
        Pick three.
        Trust me.
        ";
    
        assert_eq!(vec!["Rust:", "Trust me."], search_case_insensitive(query, contents));
    }
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut results = Vec::new();
    for line in contents.lines() {
        if line.contains(query) {
            results.push(line);
        }
    }

    results
}

pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }
    results
}

02

根据计算机的环境变量设定，决定使用不同的查找函数。

use std::{error::Error, fs, env};

pub struct Config { // 结构体、及属性；方法都需要使用 pub 改造
    // 使用结构体组合参数使之有意义
    pub query: String,
    pub filename: String,
    pub case_sensitive: bool, // 增加大小写函数调用开关
}

impl Config {
    pub fn new(args: &[String]) -> Result<Config, &'static str> {
        if args.len() < 3 {
            return Err("not enough arguments");
        }
        let query = args[1].clone();
        let filename = args[2].clone();
        let case_sensitive = env::var("CASE_SENSITIVE").is_err();
        Ok(Config { query, filename, case_sensitive })
    }
}

pub fn run(config: Config)-> Result<(), Box<dyn Error>> {
    let contents =
    fs::read_to_string(config.filename)?;

    let results = if config.case_sensitive { // 根据开关调用不同函数
        search(&config.query, &contents)
    }else {
        search_case_insensitive(&config.query, &contents)
    };
    for line in results {
        println!("{}", line);
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn case_sensitive() {
        let query = "duct";
        let content = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape";

        assert_eq!(vec!["safe, fast, productive."], search(query, content));
    }

    #[test]
    fn case_insensitive() {
        let query = "rUsT";
        let contents = "\
        Rust:
        safe, fast, productive.
        Pick three.
        Trust me.
        ";
    
        assert_eq!(vec!["Rust:", "Trust me."], search_case_insensitive(query, contents));
    }
}

pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let mut results = Vec::new();
    for line in contents.lines() {
        if line.contains(query) {
            results.push(line);
        }
    }

    results
}

pub fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    let query = query.to_lowercase();
    let mut results = Vec::new();

    for line in contents.lines() {
        if line.to_lowercase().contains(&query) {
            results.push(line);
        }
    }
    results
}

总结

这次通过给命令行增加参数配置，决定才是不同的查找匹配函数。

上一篇：Rust 头铁之路 | 采用测试驱动开发完善库功能

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