Rust字符串不区分大小写比较方法及游戏代码失效问题求助

核心问题 #

你遇到的所有输入都触发"Invalid Response"的原因是：io::stdin().read_line(&mut guess)会把输入末尾的换行符（\n）也读取到字符串中。比如你输入rock，实际guess存储的是"rock\n"，和你用来比较的"rock"、"paper"等字符串不相等，导致所有条件判断都不成立，最终走到默认的错误输出分支。

解决方案 #

读取输入后，必须先去除字符串首尾的空白字符（包括换行符、多余空格），可以使用trim()方法，之后再进行比较或转换大小写。

修复后的当前版本代码 #

use std::io;
use std::thread;
use std::time;
use rand::Rng;

fn start_next() {
    thread::sleep(time::Duration::from_secs(3));
    rps();
}

fn rps() {
    let rk = String::from("rock");
    let pp = String::from("paper");
    let sc = String::from("scissors");
    let end = String::from("end");
    
    let mut guess = String::new();
    println!("Choose one (\"end\" to quit):\n- rock\n- paper\n- scissors");
    
    io::stdin().read_line(&mut guess).expect("Unable to read line");
    // 关键修复：去除首尾空白字符（包括换行符）
    guess = guess.trim().to_string();
    
    let aichoice = ["rock", "paper", "scissors"][rand::thread_rng().gen_range(0..3)];

    // debug
    println!("\nAI chose {}", aichoice); 
    println!("You chose {}", guess);
    
    if guess.eq_ignore_ascii_case(&rk) {
        match aichoice {
            "rock" => println!("Your moves canceled out."),
            "paper" => println!("Paper defeated your rock."),
            "scissors" => println!("You defeated scissors"),
            _ => {}
        }
        start_next();
        return;
    }
    if guess.eq_ignore_ascii_case(&pp) {
        match aichoice {
            "rock" => println!("You defeated rock."),
            "paper" => println!("Your moves canceled out."),
            "scissors" => println!("Scissors defeated your paper."),
            _ => {}
        }
        start_next();
        return;
    }
    if guess.eq_ignore_ascii_case(&sc) {
        match aichoice {
            "rock" => println!("Rock defeated your scissors."),
            "paper" => println!("You defeated paper."),
            "scissors" => println!("Your moves canceled out."),
            _ => {}
        }
        start_next();
        return;
    }
    if guess.eq_ignore_ascii_case(&end) {
        return;
    }
    
    println!("Invalid response");
    start_next();
}

注：同时修复了随机数生成的写法，rand::random::<u8>() %3替换为更规范的rand::thread_rng().gen_range(0..3)，需确保Cargo.toml中添加了rand依赖。

修复后的to_lowercase+match版本代码 #

你之前的match版本除了未处理换行符外，还存在语法错误（Rust的match不需要case关键字），修复后如下：

use std::io;
use std::thread;
use std::time;
use rand::Rng;

fn rps() {
    let mut guess = String::new();
    println!("Choose one (\"end\" to quit):\n- rock\n- paper\n- scissors");
    
    io::stdin().read_line(&mut guess).expect("Unable to read line");
    // 先去除换行符，再转小写
    let guess2 = guess.trim().to_lowercase();

    let aichoice = ["rock", "paper", "scissors"][rand::thread_rng().gen_range(0..3)];

    match guess2.as_str() {
        "rock" => {
            match aichoice {
                "rock" => println!("Your moves canceled out."),
                "paper" => println!("Paper defeated your rock."),
                "scissors" => println!("You defeated scissors"),
                _ => {}
            }
        }
        "paper" => {
            match aichoice {
                "rock" => println!("You defeated rock."),
                "paper" => println!("Your moves canceled out."),
                "scissors" => println!("Scissors defeated your paper."),
                _ => {}
            }
        }
        "scissors" => {
            match aichoice {
                "rock" => println!("Rock defeated your scissors."),
                "paper" => println!("You defeated paper."),
                "scissors" => println!("Your moves canceled out."),
                _ => {}
            }
        }
        "end" => return,
        _ => println!("Invalid Response"),
    }

    thread::sleep(time::Duration::from_secs(3));
    rps();
}

额外说明 #

• trim()会去除字符串首尾的所有空白字符（包括空格、制表符、换行符），如果只想去除末尾的换行符，也可以使用trim_end()或trim_matches('\n')。
• 不区分大小写的字符串比较，除了eq_ignore_ascii_case（仅支持ASCII字符），如果需要支持非ASCII字符的大小写不敏感比较，可以使用unicase crate。

内容的提问来源于stack exchange，提问作者a human being