今天是学习rust的第五天,学习材料为官网的《The Rust Programming Language》,本笔记的内容为第12章,I/O project
Chapter 12 I/O project: Building a Command Line ProgramSeparation of Concerns for Binary Projects
将代码程序分为main.rs和lib.rs,将程序的逻辑logic移动到lib.rs 当parsing逻辑足够小时可以放在main.rs下main.rs中的函数应该有以下功能:
调用命令行parsing logic 设置其他任何的配置 调用lib.rs中的run函数 若run出现错误,则处理错误src/main.rs
use std::env; //这个库不支持错误的Unicode编码,如果想要支持则需要std::env::arg_os
use std::process;
use minigrep::Config;
fn main() {
let args: Vec = env::args().collect(); //使得命令行工具得以读取任意命令,并且将其传递、转换为一个vector
//println!("{:?}", args);
let config = Config::new(&args).unwrap_or_else(|err|{ //unwrap_or_else可以帮助我们实现用户化的错误信息返回
println!("Problem parsing arguments: {}", err);
process::exit(1);
});
//println!("Searching for {}", config.query);
//println!("In the file {}", config.filename);
//调用run,运行读取文件等操作,main中处理错误:相当于lib中的函数被调用,如果出现错误则把错误抛给main
if let Err(e) = minigrep::run(config) {
println!("Application error: {}", e);
process::exit(1);
}
}
lib.rs
use std::fs; //处理文件的库
use std::error::Error;
use std::env;
pub struct Config{
pub query: String,
pub filename: String,
pub case_sensitive: bool,
}
pub fn run(config: Config) -> Result<(), Box> { //Box会返回一个类型,实现error trait,且我们不需指明这个类型
let contents = fs::read_to_string(config.filename)?; //问号会从当前的函数返回错误值,给调用者处理
let results = if config.case_sensitive {
search(&config.query, &contents)
}else{
search_case_insensitive(&config.query, &contents)
};
for line in results {
println!("{}", line);
}
Ok(())
}
impl Config{
pub fn new(args: &[String]) -> Result{
if args.len() < 3{
//panic!("not enough arguments!");
return Err("not enough arguments!");
}
let query = args[1].clone();
let filename = args[2].clone();
let case_sensitive = env::var("CASE_INSENSITIVE").is_err(); //调动env::var来返回一个Result
Ok(Config{ query, filename, case_sensitive })
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn case_sensitive() {
let query = "duct";
let contents = "\
Rust:
safe, fast, productive.
Pick three.
Duct tape.";
assert_eq!(
vec!["safe, fast, productive."],
search(query, contents)
);
}
#[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(query: &str, contents: &'a str) -> Vec{ //检索函数
let mut results = Vec::new();
for line in contents.lines(){ //方法line返回一个iter,查找每一行
if line.contains(query){
results.push(line);
}
}
results
}
pub fn search_case_insensitive(query: &str, contents: &'a str) -> Vec {
let query = query.to_lowercase(); //将query中的内容进行小写化
let mut results = Vec::new();
for line in contents.lines() {
if line.to_lowercase().contains(&query) {
results.push(line);
}
}
results
}
设置环境变量:
CASE_INSENSITIVE=1 cargo run to poem.txt
注意此处我们不关心这个环境变量具体是多少,我们只关心他是否被设置了
peom.txt
是文件,里面有一首诗。本章的命令行程序实现了读取文件、大小写敏感\不敏感搜索的任务。上述命令是在poem.txt中搜索关键字to