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-// This is similar to the previous `from_into` exercise. But this time, we'll
-// implement `FromStr` and return errors instead of falling back to a default
-// value. Additionally, upon implementing `FromStr`, you can use the `parse`
-// method on strings to generate an object of the implementor type. You can read
-// more about it in the documentation:
-// https://doc.rust-lang.org/std/str/trait.FromStr.html
-
-use std::num::ParseIntError;
-use std::str::FromStr;
-
-#[derive(Debug, PartialEq)]
-struct Person {
- name: String,
- age: u8,
-}
-
-// We will use this error type for the `FromStr` implementation.
-#[derive(Debug, PartialEq)]
-enum ParsePersonError {
- // Incorrect number of fields
- BadLen,
- // Empty name field
- NoName,
- // Wrapped error from parse::<u8>()
- ParseInt(ParseIntError),
-}
-
-// TODO: Complete this `FromStr` implementation to be able to parse a `Person`
-// out of a string in the form of "Mark,20".
-// Note that you'll need to parse the age component into a `u8` with something
-// like `"4".parse::<u8>()`.
-//
-// Steps:
-// 1. Split the given string on the commas present in it.
-// 2. If the split operation returns less or more than 2 elements, return the
-// error `ParsePersonError::BadLen`.
-// 3. Use the first element from the split operation as the name.
-// 4. If the name is empty, return the error `ParsePersonError::NoName`.
-// 5. Parse the second element from the split operation into a `u8` as the age.
-// 6. If parsing the age fails, return the error `ParsePersonError::ParseInt`.
-impl FromStr for Person {
- type Err = ParsePersonError;
-
- fn from_str(s: &str) -> Result<Self, Self::Err> {}
-}
-
-fn main() {
- let p = "Mark,20".parse::<Person>();
- println!("{p:?}");
-}
-
-#[cfg(test)]
-mod tests {
- use super::*;
- use ParsePersonError::*;
-
- #[test]
- fn empty_input() {
- assert_eq!("".parse::<Person>(), Err(BadLen));
- }
-
- #[test]
- fn good_input() {
- let p = "John,32".parse::<Person>();
- assert!(p.is_ok());
- let p = p.unwrap();
- assert_eq!(p.name, "John");
- assert_eq!(p.age, 32);
- }
-
- #[test]
- fn missing_age() {
- assert!(matches!("John,".parse::<Person>(), Err(ParseInt(_))));
- }
-
- #[test]
- fn invalid_age() {
- assert!(matches!("John,twenty".parse::<Person>(), Err(ParseInt(_))));
- }
-
- #[test]
- fn missing_comma_and_age() {
- assert_eq!("John".parse::<Person>(), Err(BadLen));
- }
-
- #[test]
- fn missing_name() {
- assert_eq!(",1".parse::<Person>(), Err(NoName));
- }
-
- #[test]
- fn missing_name_and_age() {
- assert!(matches!(",".parse::<Person>(), Err(NoName | ParseInt(_))));
- }
-
- #[test]
- fn missing_name_and_invalid_age() {
- assert!(matches!(
- ",one".parse::<Person>(),
- Err(NoName | ParseInt(_)),
- ));
- }
-
- #[test]
- fn trailing_comma() {
- assert_eq!("John,32,".parse::<Person>(), Err(BadLen));
- }
-
- #[test]
- fn trailing_comma_and_some_string() {
- assert_eq!("John,32,man".parse::<Person>(), Err(BadLen));
- }
-}