二进制程序关注点分离的指导性原则

  • 将程序拆分为 main.rs 和 lib.rs，将业务逻辑放入 lib.rs
  • 当命令行解析逻辑较少时，将它放在 main.rs 也行

  • 当命令行逻辑边复杂时，需要将它从 main.rs 提取到 lib.rs

    经过上述拆分，留在 main 的功能有：

  • 使用参数值调用命令行解析逻辑

  • 进行其他配置
  • 调用 lib.rs 中的 run 函数
  • 处理 run 函数可能出现的错误

    改进模块化

    ```rust use std::env; use std::fs;

fn main() { let args: Vec = env::args().collect();

  1. let config = Config::new(&args);
  3. let contents =
  4.     fs::read_to_string(config.filename).expect("Something went wrong reading the file");
  6. println!("With text:\n{}", contents);

}

struct Config { query: String, filename: String, }

impl Config { fn new(args: &[String]) -> Config { let query = args[1].clone(); let filename = args[2].clone(); Config { query, filename } } }

  1. <a name="SRH3F"></a>
  2. ## 错误处理
  3. ```rust
  4. use std::env;
  5. use std::fs;
  6. use std::process;
  8. fn main() {
  9.     let args: Vec<String> = env::args().collect();
  11.     let config = Config::new(&args).unwrap_or_else(|err| {
  12.         println!("Problem parsing arguments: {}", err);
  13.         process::exit(1);
  14.     });
  16.     let contents =
  17.         fs::read_to_string(config.filename).expect("Something went wrong reading the file");
  19.     println!("With text:\n{}", contents);
  20. }
  22. struct Config {
  23.     query: String,
  24.     filename: String,
  25. }
  27. impl Config {
  28.     fn new(args: &[String]) -> Result<Config, &'static str> {
  29.         if args.len() < 3 {
  30.             return Err("not enough arguments");
  31.         }
  32.         let query = args[1].clone();
  33.         let filename = args[2].clone();
  34.         Ok(Config { query, filename })
  35.     }
  36. }

优化

  1. use std::env;
  2. use std::error::Error;
  3. use std::fs;
  4. use std::process;
  6. fn main() {
  7.     let args: Vec<String> = env::args().collect();
  9.     let config = Config::new(&args).unwrap_or_else(|err| {
  10.         println!("Problem parsing arguments: {}", err);
  11.         process::exit(1);
  12.     });
  14.     if let Err(e) = run(config) {
  15.         println!("Application error: {}", e);
  16.         process::exit(1);
  17.     }
  18. }
  20. fn run(config: Config) -> Result<(), Box<dyn Error>> {
  21.     let contents = fs::read_to_string(config.filename)?;
  22.     println!("With text:\n{}", contents);
  23.     Ok(())
  24. }
  26. struct Config {
  27.     query: String,
  28.     filename: String,
  29. }
  31. impl Config {
  32.     fn new(args: &[String]) -> Result<Config, &'static str> {
  33.         if args.len() < 3 {
  34.             return Err("not enough arguments");
  35.         }
  36.         let query = args[1].clone();
  37.         let filename = args[2].clone();
  38.         Ok(Config { query, filename })
  39.     }
  40. }

拆分

  1. // main.rs
  2. use minigrep::Config;
  3. use std::env;
  4. use std::process;
  6. fn main() {
  7.     let args: Vec<String> = env::args().collect();
  9.     let config = Config::new(&args).unwrap_or_else(|err| {
  10.         println!("Problem parsing arguments: {}", err);
  11.         process::exit(1);
  12.     });
  14.     if let Err(e) = minigrep::run(config) {
  15.         println!("Application error: {}", e);
  16.         process::exit(1);
  17.     }
  18. }
  1. // lib.rs
  2. use std::error::Error;
  3. use std::fs;
  5. pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
  6.   let contents = fs::read_to_string(config.filename)?;
  7.   println!("With text:\n{}", contents);
  8.   Ok(())
  9. }
  11. pub struct Config {
  12.   pub query: String,
  13.   pub filename: String,
  14. }
  16. impl Config {
  17.   pub fn new(args: &[String]) -> Result<Config, &'static str> {
  18.     if args.len() < 3 {
  19.       return Err("not enough arguments");
  20.     }
  21.     let query = args[1].clone();
  22.     let filename = args[2].clone();
  23.     Ok(Config { query, filename })
  24.   }
  25. }