管理机器人工厂设置.

当机器人从工厂车间出来时，他们没有名字。

第一次启动时，会生成一个随机名称，格式为两个大写字母后跟三个数字，如 RX837 或 BC811。

每隔一段时间我们就需要将机器人重置为出厂设置，这意味着他们的名字会被擦除。下次你问，它会以一个新的随机名称回复。

名称必须是随机的:它们不应遵循可预测的顺序。随机名称表示发生碰撞的风险。您的解决方案必须确保每个现有机器人都具有唯一名称。

与 Paul Blackwell 在 gSchool 的调试会议.http://gschool.it

pub struct Robot;

impl Robot {
   pub fn new() -> Self {
       unimplemented!("Construct a new Robot struct.");
   }

   pub fn name(&self) -> &str {
       unimplemented!("Return the reference to the robot's name.");
   }

   pub fn reset_name(&mut self) {
       unimplemented!("Assign a new unique name to the robot.");
   }
}

# #![allow(unused_variables)]
#fn main() {
fn assert_name_matches_pattern(n: &str) {
   assert!(n.len() == 5, "name is exactly 5 characters long");
   assert!(
       n[0..2].chars().all(|c| c >= 'A' && c <= 'Z'),
       "name starts with 2 uppercase letters"
   );
   assert!(
       n[2..].chars().all(|c| c >= '0' && c <= '9'),
       "name ends with 3 numbers"
   );
}

fn assert_name_is_persistent(r: &Robot) {
   // The type system already proves this, but why not.
   let n1 = r.name();
   let n2 = r.name();
   let n3 = r.name();
   assert_eq!(n1, n2);
   assert_eq!(n2, n3);
}

#[test]
fn test_name_should_match_expected_pattern() {
   let r = Robot::new();
   assert_name_matches_pattern(r.name());
}

#[test]
//#[ignore]
fn test_name_is_persistent() {
   assert_name_is_persistent(&Robot::new());
}

#[test]
//#[ignore]
fn test_different_robots_have_different_names() {
   let r1 = Robot::new();
   let r2 = Robot::new();
   assert_ne!(r1.name(), r2.name(), "Robot names should be different");
}

#[test]
//#[ignore]
fn test_new_name_should_match_expected_pattern() {
   let mut r = Robot::new();
   assert_name_matches_pattern(r.name());
   r.reset_name();
   assert_name_matches_pattern(r.name());
}

#[test]
//#[ignore]
fn test_new_name_is_persistent() {
   let mut r = Robot::new();
   r.reset_name();
   assert_name_is_persistent(&r);
}

#[test]
//#[ignore]
fn test_new_name_is_different_from_old_name() {
   let mut r = Robot::new();
   let n1 = r.name().to_string();
   r.reset_name();
   let n2 = r.name().to_string();
   assert_ne!(n1, n2, "Robot name should change when reset");
}

#}

# #![allow(unused_variables)]
#fn main() {
extern crate rand;
use rand::{thread_rng, Rng};

pub struct Robot {
   name: String,
}

fn generate_name() -> String {
   let mut s = String::with_capacity(5);
   static LETTERS: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
   static NUMBERS: &'static [u8] = b"0123456789";
   for _ in 0..2 {
       s.push(thread_rng().choose(LETTERS).unwrap().clone() as char);
   }
   for _ in 0..3 {
       s.push(thread_rng().choose(NUMBERS).unwrap().clone() as char);
   }
   s
}

impl Robot {
   pub fn new() -> Robot {
       Robot {
           name: generate_name(),
       }
   }

   pub fn name<'a>(&'a self) -> &'a str {
       &self.name[..]
   }

   pub fn reset_name(&mut self) {
       self.name = generate_name();
   }
}

#}