如何將字符串轉換爲枚舉？

Question

我的original approach是創建一個名爲to_str()的方法，它將返回一個分片，但我不確定這是否是正確的方法。

enum WSType { 
ACK, 
REQUEST, 
RESPONSE, 
} 

impl WSType { 
    fn to_str(&self) -> &str { 
    match self { 
     ACK => "ACK", 
     REQUEST => "REQUEST", 
     RESPONSE => "RESPONSE",    
    } 
    } 
} 

fn main() { 
    let val = "ACK"; 
    // test 
    match val { 
    ACK.to_str() => println!("ack"), 
    REQUEST.to_str() => println!("ack"), 
    RESPONSE.to_str() => println!("ack"), 
    _ => println!("unexpected"), 
    } 
} 

Answer 1

正確的做法是實施FromStr：

#[derive(Debug)] 
enum WSType { 
    Ack, 
    Request, 
    Response, 
} 

impl std::str::FromStr for WSType { 
    type Err = &'static str; 

    fn from_str(s: &str) -> Result<Self, Self::Err> { 
     match s { 
      "ACK" => Ok(WSType::Ack), 
      "REQUEST" => Ok(WSType::Request), 
      "RESPONSE" => Ok(WSType::Response), 
      _ => Err("not a valid value"), 
     } 
    } 
} 

fn main() { 
    let as_enum: WSType = "ACK".parse().unwrap(); 
    println!("{:?}", as_enum); 
} 

要打印值，實現Display或Debug（我在這裏得到的話）。實施Display也會給你.to_string()。