预期字符串，匹配可选字符串时找到 &str [英] Expected String, found &str when matching an optional string

问题描述

我正在尝试在 Rust 中编写一个简单的函数，它会询问用户一个问题，期望得到你"或我"的回答.如果用户回答错误，它应该返回一个布尔值或再次询问.我想出了:

I am trying to write a simple function in Rust that will ask user a question expecting answer of "you" or "me". It should return a boolean value or ask again if the user answers wrong. I came up with:

fn player_starts() -> bool {                                                    
    println!("Who will start (me/you)");                                       
    loop {                                                                      
        let input = readline::readline(">");                                    
        match input {                                                           
            Some("me") => return true,                                          
            Some("you") => return false,                                        
            _ => None,                                                          
        }                                                                          
    }                                                                           
}       

我得到的是:

error: mismatched types:
 expected `collections::string::String`,
    found `&'static str`
(expected struct `collections::string::String`,
found &-ptr) [E0308]

有什么方法可以强制文字在这里起作用，或者有什么更好的方法来实现我的目标?

Is there some way to coerce the literal to work here or is there some better way to achieve my goal?

推荐答案

这应该有效:

fn player_starts() -> bool {                      
    println!("Who will start me/you)");                    
    loop {
        let input = readline::readline(">");
        match input.as_ref().map(String::as_ref) {
            Some("me") => return true,
            Some("you") => return false,
            _ => ()
        }
    }
}

注意 match 语句中的表达式，我们将其中的 Option 转换为 Option<&str>.

Note the expression in the match statement, where we convert from an Option<String> to an Option<&str>.

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