rust13.枚举和模式匹配

  //这一部分应当放在函数体内部，因为有分号，此处为了方便第5部分没有修改
  //1.类似C方法定义
  enum IpAddKind {
    V4,
    V6,
  }
  struct IpAddr {
    kind: IpAddKind,
          address: String,
  };
  let i1 = IpAddr {
    kind: IpAddKind::V4,
          address: String::from("127.0.0.1"),
  };
  let i2 = IpAddr {
    kind: IpAddKind::V6,
          address: String::from("::1"),
  };
  //2. 以rust方式进行定义
  enum IpAdd2 {
       V4(String),
       V6(String),
    };
    let i1 = IpAdd2::V4(String::from("127.0.0.1"));
    let i2 = IpAdd2::V6(String::from("::1"));
  //3.可以是不同类型
  enum IpAddr3 {
      V4(u8,u8,u8,u8),
      V6(String),
    };
    let i1 = IpAddr3::V4(127,0,0,1);
    let i2 = IpAddr3::V6("String::from("::1)");
  //4.经典用法
  enum Message {
      Quit,
      Move{x: i32,y: i32}, //move是一个结构体
      Write(String),
      Change(i32,i32,i32),
    };
  //等同于
  //struct QuitMessage; //类单元结构体
  //struct MoveMessage {
  //    x: i32,
  //    y: i32,
  // }
  // struct WriteMessage(String)
  //struct Change(i32,i32,i32)
  //5.枚举类型的方法和match
impl Message {
    fn prin(&self) {
        match *self {  //解引用
                Message::Quit => println!("Quit"),
                Message::Move{x,y} => println!("Move x = {},y = {}",x,y),
                Message::Change(a,b,c) => println!("Change a = {}, b = {},c = {}",a,b,c),
                _ => println!("Write")
                //此处会报错，因为这是一个引用，而真正想要的是string类型
                //Message::Write(&s) => println!("Write = {}",s)
          }
      }
  }
fn main() {
  
   let quit = Messag::Quit;
   quit.prin();
   let mo = Messag::Move {x: 10 , y: 20};
   mo.prin();
   let wri = Message::Write(String::from("Hello"));
   wri.prin();
   let change = Message::Change(1,2,3);
   change.prin();
}