finish from_str

Author: ChaonanShen

exercises/conversions/from_str.rs

@@ -31,8 +31,6 @@ enum ParsePersonError {
     ParseInt(ParseIntError),
 }
 
-// I AM NOT DONE
-
 // Steps:
 // 1. If the length of the provided string is 0, an error should be returned
 // 2. Split the given string on the commas present in it
@@ -52,6 +50,17 @@ enum ParsePersonError {
 impl FromStr for Person {
     type Err = ParsePersonError;
     fn from_str(s: &str) -> Result<Person, Self::Err> {
+        if s.is_empty() { return Err(ParsePersonError::Empty); }
+        let parts: Vec<_> = s.split(',').collect();
+        if parts.len() != 2 {
+            return Err(ParsePersonError::BadLen);
+        }
+        let (name, age_str) = (parts[0], parts[1]);
+        if name.is_empty() { return Err(ParsePersonError::NoName); }
+        match age_str.parse::<usize>() {
+            Err(e) => Err(ParsePersonError::ParseInt(e)),
+            Ok(age) => Ok(Person{name: name.to_string(), age: age}),
+        }
     }
 }